A man in a wheelchair who was airing grievances set off a homemade bomb in a crowded terminal at Beijing's main airport on Saturday evening, injuring himself but no one else, Chinese state media and witnesses said.

Order was quickly restored and no flights were affected by the explosion at the airport's main international terminal, state-run China Central Television said on its microblog.  

The official Xinhua News Agency said a wheel-chaired Chinese man set off the device outside the arrivals exit of Terminal 3 at Beijing Capital International Airport at around 6:24 p.m. It said the man was being treated for injuries, but that no one else was hurt in the explosion.   

``The explosion sound was loud,'' said a witness who gave only his family name, Chen. He said he was only 25 meters (27 yards) away from the explosion when it occurred.   

Chen said there was only one explosion, and that the terminal was crowded with people. ``Since there was no second explosion, many people took out their phones and gathered near the explosion spot to take photos,'' he said.   

He said police responded to the explosion immediately.   

Another witness, who gave only his last name, Qing, said there was no one around the man when he set off the bomb.   

``It sounded like the sound of big firecrackers,'' said Qing, who was about 60 meters (66 yards) away from the explosion. ``We couldn't see really what happened afterward. There was a lot of smoke and the police arrived very fast.''   

CCTV identified the man in the wheelchair as Ji Zhongxing, born in 1979 and from the eastern province of Shandong.   

It was not immediately clear why the man allegedly set off the bomb, but Xinhua said he was stopped from handing out leaflets airing his complaints before setting off the bomb. Xinhua, which cited an initial police investigation, did not say what his complaints were.   

In an online blog entry from 2006, a writer who provides the same name, the same year of birth and the same hometown in Shandong province as Ji complained of his disabilities resulting from cruel beatings by security personnel in the southern province of Guangdong. He said he had been seeking justice and compensation, but to no avail.   

``Because we are peasants and we are poor, no one is willing to help us,'' the author wrote in the entry, which was the latest one in the blog.   

The blog, which was available immediately after the explosion, was removed within hours, and it was not possible to verify its authenticity.   

Photos posted by CCTV on its microblog showed the area near the arrivals exit empty and filled with smoke. One photo showed medical staff and police officers gathering at one spot, with a wheelchair sitting on its side a few steps away.   

Reached by phone, the airport's news office said it was not aware of the explosion, and airport police declined to answer questions.   

Terminal 3, which opened in 2008 just ahead of the Beijing Olympics, is the airport's hub for international flights. United Airlines and American Airlines are among the carriers that operate out of the terminal.   

United Airlines spokeswoman Karen May in Chicago said the explosion did not affect its operations. American Airlines could not be reached immediately for comment.    

Associated Press TV producer Aritz Parra contributed to this report. (AP)