BEIJING (AP) -- A man set himself on fire in front of the office where citizens go to petition for help from China's legislature, a witness said Friday.

Self-immolations have happened occasionally in recent years in Beijing, usually as last-ditch protests from people upset the government has not addressed their complaints.

"A man who looked 40 to 50 set himself on fire in front of the petition office of National People's Congress Building in Beijing on Wednesday," said Li Jian, who witnessed the incident.

"He poured gasoline on his body, set himself on fire with a lighter and was shouting: 'My son was murdered, I was set up,"' Li said.

Calls to the local police office and to the petition office were not answered Friday.

Li, also a petitioner from Hunan province seeking help to solve his daughter's murder, said the man was by himself so there was no one who could say what his background was.

"He was screaming and terribly burned," Li said. "The guards wrapped up his body with a big piece of cloth and sent him to hospital. We heard he died."

Last summer, a construction worker hoping to get back pay owed to him set himself on fire on Tiananmen Square, but the flames were quickly extinguished and the man was hospitalized.

Security around the square, historically a gathering place for protests, is usually extremely tight and such incidents are now rare.

On the square in 2003, a laid-off worker set himself on fire, two weeks after another man had set himself ablaze to protest the demolition of his home. Both were hospitalized for injuries.

In January 2001, five people set themselves on fire on Tiananmen in an incident that Chinese authorities blamed on the banned Falun Gong spiritual movement. Two of the people -- a woman and her 12-year-old daughter -- died.