NEW YORK - Police across New York City are stepping up security at high-profile locations as the Islamic State terror group claims responsibility for Monday's deadly bombing outside of an Ariana Grande concert in Manchester, England.

Police in England have arrested a 23-year-old man in connection with the attack, but they have not released any details about him.

Police say he was arrested in south Manchester Tuesday.

British police now say it appears to be the work of a suicide bomber, who has been idenitifed as Salman Abedi.

Chaos spread through Manchester Arena and concertgoers went running for their lives after an improvised explosive device went off outside the venue at the end of the show.

At least 22 people were killed including several children, and dozens more were injured.

The Islamic state group claims one of its members planted bombs in the middle of crowds. 

But police believe the attacker used an improvised explosive device and killed himself.

Dan Coats, U.S. director of intelligence, says the Islamic State connection has not yet been verified.

Investigators are now trying to figure out if the bomber had any accomplices.

"We have been treating this as a terrorist incident and we believe at this stage the attack last night was conducted by one man. The priority is to establish whether he was acting alone or as part of a network," said Ian Hopkins of the Greater Manchester Police.

"We were in the concert, she just finished she walked off and we all got up to leave and we all went down the stairs into the park and there was just this huge bang so everyone just looked at each other and there was just a mad rush to get out," said one concert goer.

Ariana Grande, who was not hurt, posted to Twitter after the incident.

British Prime Minister Theresa May is condemning the attack.

"We struggle to comprehend the warped and twisted mind that sees a room packed with young children not as a scene to cherish, but as an opportunity for carnage. But we can continue to resolve to thwart such attacks in future, to take on and defeat the ideology that often fuels this violence and if it turns out to be others responsible for this attack, to seek them out and bring them to justice," May said.

In a tweet Tuesday, President Donald Trump said, "We stand in absolute solidarity with the people of the United Kingdom."

Extra police were sent to Madison Square Garden Monday night, and Governor Andrew Cuomo says the state is boosting security at airports, bridges, tunnels and mass transit systems.

Mayor Bill de Blasio also says the NYPD is closely monitoring the developments in England.