Police have linked a sex assault from Labor Day morning to a string of attacks in Upper Manhattan.

The latest incident happened at West 147th Street and Saint Nicholas Avenue.

Police say a 28-year-old woman told them she was assaulted around 1 a.m. Monday after the suspect came into her apartment and threatened her with a knife.

They say he then took off with cash and other items.

Police are handing out flyers in Harlem that feature a sketch and two photos of the suspect, to try to hunt the assaulter who has hit four times since August 1.

The associated attacks took place at West 144th and Convent Avenue, West 148th and Broadway and West 158th and Riverside Drive. The other victims were 23, 59 and 69 years old. In all cases, he threatened the women with a knife.

There is a $12,000 reward for information leading to an arrest and conviction.

"Keeping windows locked at night more and generally being wary," said Nir Krakauer, who lived in the building where the latest attack took place.

"I look out for my sisters, they're 14 and 15 years old," said another resident of the building. "So I'm scared for my sisters, you know? I have to escort them out from school. I'm terrified."

"I feel terrible. I'm just hoping he doesn't come to me," said local Edna Kirk. "I feel awful bad about this and I hope they hurry up and catch this guy."

Authorities released two weeks ago a surveillance photo of the suspect, seen above. He is described as 5-feet-5-inches tall and around 150 pounds.

"There are people who get up in the morning, the same way we get up to work, to plot things against other people and to take things from them," said a local woman. "So we have to always be careful."

Anyone with information on the suspect should contact the Crime Stoppers hotline at 1-800-577-TIPS, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com.