Washington  - A lone gunman went on a rampage at an immigration services centre in New York state Friday killing 13 people before shooting himself in the head, police said.

Another four people were critically wounded by the man, who was later identified as Jiverly Wong, 42, a Vietnamese immigrant, a senior law enforcement office told the New York Times.

The slaughter took place at the American Civic Association Building, which provides services to refugees and immigrants and classes to prepare them for US citizenship, in Binghamton, about 225 kilometres northwest of New York city.

Binghamton Mayor Matthew Ryan said the gunman had recently lost his job and had apparently told his family that he wasn't happy with his life.

In an interview with broadcaster MSNBC, Ryan said that the city, with a population of 35,000 was also one in which 32 languages were spoken in public schools and where "immigrants are an important fabric of our lives."

"Only one homicide was reported here in the last year," he said, adding that the close-knit community was in shock.

Joseph Zikuski, police chief of Binghamton, said two semi- automatic handguns and a satchel of ammunition were found on the suspect's body inside the centre where immigrants were taking citizenship and language classes.

Thirty-seven people escaped the lethal attack, including 26 people who fled to the basement with their cell phones when they heard gunshots, Zikuski said. Most of the survivors could not speak English.

They locked themselves in the boiler room, following instructions from police on their cell phones on how to barricade the door.

"I heard shootings, very long time, about five minutes, and I was thinking when it will be stopped, but it was continued. No screaming, yelling, just silence, shooting, silence, shooting, silence," Zhanar Tokhtabayeba, who was taking an English class, told CNN.

It took nearly four hours for SWAT teams to clear every room in the building and police had to give those trapped continued reassurances "that we would come and get them. They were antsy and wanted to come out," the police chief said.

"The attack obviously was premeditated," Zikuski said, referring to a borrowed car that was parked behind the building to block people from leaving by the back door.

"He barricaded this door so no one could get out," the police chief said.

The killer, who was "no stranger" to the centre, then walked around to enter by the front, shooting two receptionists with a hand gun. One of them was killed, and the second fell to the floor and pretended to be dead.

After the gunman left the reception area to start shooting in the next room, she crawled under a desk and called police.

She was the only living witness who could identify the killer, and police debriefed her on the way to the hospital, where she was undergoing surgery for gunshot wounds in her stomach, Zikuski said.

The alleged shooter Wong lived in California from 2000 to 2007 and worked as a driver. One day he just stopped going to work, a former colleague said, describing him as a man who rarely socialized. His supervisor said he was a hard worker who never called in sick.

"He went there purposefully and intentionally," Representative Maurice Hinchey, whose district includes Binghamton, told the Times. "I can't believe that this wonderful, beautiful little city would have this kind of experience."

New York Governor David Paterson, who rushed to the scene, declared the shooting "a tragic day for New York."

He referred to all the recent mass shootings in the US over the past few months - a murder-suicide in California in an immigrant family from India, the killing of eight people at a nursing home in Carthage, North Carolina, and the slaying of four California police officers.

US President Barack Obama, in Europe attending the NATO summit, released a statement saying he and his wife Michelle were "shocked and deeply saddened" by the "senseless violence in Binghamton."

"We've got to figure out a way to deal with this senseless, senseless violence," said US Vice President Joe Biden at a conference in New York city.