KIEV, Ukraine (AP) — The Latest on raised tensions between Russia and Ukraine (all times local):

7:15 p.m.

The Kremlin says it has not been notified of a cancellation of the much-anticipated meeting between Russian President Vladimir Putin and U.S. President Donald Trump.

Russian news agencies on Thursday quoted Dmitry Peskov, Putin's spokesman, as saying that the Kremlin only learnt about the cancellation from Trump's tweet. He says the Russian delegation is already on its way to the G-20 summit in Argentina.

Peskov said the cancellation means that Putin will have "a couple of more hours" for "useful meetings" with other leaders of the world's 20 largest economies.

Trump abruptly canceled the meeting on Thursday, saying in a tweet that it is not appropriate for him to meet Putin as Russia still has not returned three Ukrainian vessels it seized on Sunday. Russia has also detained 24 Ukrainian seamen.

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6:30 p.m.

Ukrainian border guards say all non-Ukrainians will be barred from crossing into the Russia-occupied Crimean peninsula by land after martial law went into effect.

Ukraine imposed martial law in the country for 30 days earlier this week after Russian border guards opened fired on three Ukrainian vessels in the Black Sea and seized the ships and their crews.

Border Guard Service spokesman Andriy Demchenko said on Ukrainian television that Ukraine is closing the border crossing into Crimea for all foreigners.

While it is still possible to fly into Crimea from Russia or drive in on the new bridge from Russia's south, Ukraine considers that a violation of its borders.

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5:15 p.m.

The Ukrainian intelligence agency says a Russian fighter jet and a helicopter fired rockets Sunday at three Ukrainian ships before they were captured near Russia-occupied Crimea.

Russian border guard ships rammed into and fired on the Ukrainian vessels Sunday as they were trying to make their way via the Kerch Strait to the Sea of Azov. Russia insisted that the vessels were violating its border while Ukraine says it was following international maritime rules and that the ships were well in the international waters.

SBU deputy chief Oleh Frolov told reporters Thursday that a Russian Su-30 fighter jet and a Ka-52 attack helicopter fired four rockets on the ships. He says "it's a miracle the Ukrainian seamen have survived."

The use of the Russian fighter jet and the helicopter was not previously reported.

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3:30 p.m.

Ukraine's Ministry of Infrastructure says Russia has blocked 35 merchant ships from leaving or entering the Sea of Azov, a claim the Kremlin has denied.

The ministry said 18 ships were stuck in the Black Sea waiting to pass through the Kerch Strait into the Sea of Azov, while another 17 vessels were unable to sail out of Ukrainian ports of Mariupol and Berdyansk on the Sea of Azov.

Kremlin spokesman Dmitry Peskov insisted that Russian authorities haven't imposed any restrictions, and that the logjam could be linked to poor weather.

Tensions between Russia and Ukraine have escalated after the weekend incident in which the Russian coast guard fired on and seized three Ukrainian navy vessels and their crews near the Kerch Strait.

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3:05 p.m.

Ukraine's president says the government will impose unspecified restrictions on Russian citizens in response to the seizure of three Ukrainian vessels and their crews.

President Petro Poroshenko said that the one-month period of martial law introduced this week in Ukraine wouldn't restrict travel, cash withdrawals or currency purchases by Ukrainians but Russians will face some constraints.

The Ukrainian leader tweeted Thursday that "there will be restrictions regarding Russian citizens, which I believe are quite justified." He did not elaborate.

Ukrainian authorities have already denied entry to an increased number of Russians following the weekend incident.

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2:05 p.m.

German Chancellor Angela Merkel says she's not backing off plans for a joint pipeline with Russia, but is pledging to ensure Ukraine remains a transit country for Russian natural gas.

Her comments follow the seizure of Ukrainian ships by Russia on Sunday which has prompted Ukrainian President Petro Poroshenko to argue for further pressure being put on Moscow.

He told Bild newspaper in an interview published Thursday that there needs to be increased pressure on Moscow, including stopping the construction of the Nord Stream 2 pipeline, which is being built under the Baltic Sea and would bypass Ukraine to deliver gas directly to Germany.

Merkel told a Ukrainian business forum in Berlin that the pipeline would go ahead, but that Germany would "ensure Ukraine remains an important transit country."

She noted that Germany could control how much fuel was pumped through the pipeline.

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10:50 a.m.

NATO says it already has a strong presence in the Black Sea region, after Ukraine President Petro Poroshenko urged members of the military alliance like Germany to send warships amid tensions with Russia.

Spokeswoman Oana Lungescu said Thursday that NATO ships routinely patrol and exercise in the Black Sea, noting that NATO ships have spent 120 days there this year compared to 80 in 2017.

She said several NATO allies conduct air policing and reconnaissance flights in the region, and that members Bulgaria, Romania, and Turkey border the Black Sea and have their own military equipment deployed.

Lungescu said "there is already a lot of NATO in the Black Sea, and we will continue to assess our presence in the region."

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10:10 a.m.

German Chancellor Angela Merkel says she plans to press Russian President Vladimir Putin at this weekend's G-20 summit in Argentina about his country's seizure of three Ukrainian ships and their crews.

Merkel told a Ukrainian business summit in Berlin on Thursday that Germany is urging the release of the ships and crews and that she would confront Putin at the summit.

She says "we can only resolve this in talks with one another because there is no military solution to all of these conflicts."

Merkel says that beyond Ukraine, Russia has been aggressive in several other nations creating "a belt of countries that cannot develop in the way they want and we can't, as Germans, close our eyes to that."

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9:45 a.m.

The Kremlin has sharply criticized the Ukrainian president's plea for NATO to deploy naval ships to the Sea of Azov amid a standoff with Russia.

President Petro Poroshenko made the call in an interview with the German daily Bild published Thursday, hoping that NATO countries "are now ready to relocate naval ships to the Sea of Azov in order to assist Ukraine and provide security."

Kremlin spokesman Dmitry Peskov said that Poroshenko's request is "clearly aimed at provoking further tensions" and driven by the Ukrainian leader's "electoral and domestic policy motives."

In Sunday's confrontation, Russian ships fired on and seized three Ukrainian vessels and their crews trying to pass into the Sea of Azov through the Kerch Strait between Russia's mainland and Crimea, which it annexed from Ukraine.

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8:15 a.m.

Turkish President Recep Tayyip Erdogan says he has discussed the possibility of a Turkish mediation to resolve tensions between Russia and Ukraine in the Sea of Azov.

Erdogan made the comments early Thursday, hours after he held separate telephone conversations with Russian President Vladimir Putin and Ukrainian President Petro Poroshenko.

The Turkish leader said: "Can we assume a mediator role? We discussed this subject with both sides."

Erdogan said he would hold more talks concerning the standoff with both Putin and U.S. President Donald Trump on the sidelines of the G-20 summit meeting in Buenos Aires.

Tensions between Russia and Ukraine flared on Sunday, when Russian border guards fired on three Ukrainian vessels and seized the ships and the crew.

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7:55 a.m.

The Ukrainian president is urging NATO to deploy naval ships to the Sea of Azov amid a standoff with Russia.

President Petro Poroshenko made the call in an interview with the German daily Bild published Thursday, saying that "we hope that states within NATO are now ready to relocate naval ships to the Sea of Azov in order to assist Ukraine and provide security."

In Sunday's confrontation, the Russian coast guard fired on and seized three Ukrainian vessels that sought to pass from the Black Sea into the Sea of Azov through the Kerch Strait, between Russia's mainland and the Crimean Peninsula it annexed from Ukraine.

Ukraine insisted that its vessels were operating in line with international maritime rules, while Russia said they had failed to get permission to pass.

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