The FBI on Saturday ruled out Pakistani Taliban militant leader Baituallah Mehsud's claim that he was responsible for an attack on a US immigration assistance center in New York state in which 14 people were killed.

"Based on the evidence, we can firmly discount that claim," FBI spokesman Richard Kolko said.

A man armed with two handguns killed 13 people at an immigrant services center on Friday before apparently turning the gun on himself, authorities in Binghamton, New York, said.

Representative Maurice Hinchey, whose district includes Binghamton, told the New York Times that indications were the gunman was an immigrant from Vietnam.

Mehsud told Reuters in Pakistan earlier Saturday that his group was responsible. "I accept responsibility. They were my men. I gave them orders in reaction to US drone attacks," Mehsud said by telephone from an undisclosed location.