But the Qiaojia county government is insisting Zhao, a labourer with a wife and young child, was the bomber who set off the Thursday morning blast in Baihetan that was first reported to be a protest against forced demolition by local authorities.

Its explanation has failed to satisfy residents and internet users because the bombing had initially been attributed to a woman.

Zhao, who was relatively new to the area, was not known to have any conflict with the government.

In addition, one man whose wife died in the blast and who was among those injured while waiting in line at the community office does not recall seeing a man matching Zhao's description.

Originally from Baogunao, more than a three-hour drive from Qiaojia, Zhao moved to Baihetan three years ago and worked as a day labour and motorcycle taxi driver.

Yesterday his photo identity card and registration card with the local Communist Youth League could be seen in his run-down tiny apartment.

A green uniform hanging on the wall and a pair of paramilitary shoulder ranks on his wooden bed suggested Zhao may have at one time been a non-commissioned officer in the Armed Police. Some women's shoes, toys and books on pregnancy care and Chinese chess were lying on the floor.

Neighbour Wang Yongqiang, 48, accused the county government of making Zhao a scapegoat.

'If Qiaojia government does not immediately rectify its way of handling relocation, more tragedies are sure to occur,' Wang said.

On Friday evening, Qiaojia county public security officials played closed-circuit television footage from around the time of the explosion to reporters from Xinhua and People's Daily's online news portal.

The outlets said footage showed a man with messy hair, multiple layers of clothing and backpack walking slowly towards Baihetan township's Huaqiao community office.

The man lingered in its outdoor courtyard for about four minutes. News reports yesterday said he then walked inside the community office and approached the crowd.

The footage shows an explosion originating in the man's vicinity at 9.04am, blowing the man's body apart. Authorities said they had found evidence at the scene matching Zhao's DNA.

The Xinhua report said Zhao had a criminal record, though authorities could not yet provide a motive. It quoted Qiaojia county party secretary Fang Zonghui describing him as a sociopath known for extreme behaviour, a pessimistic attitude and a hatred towards society.

But Li Weiyou who lost his wife and a male relative in the blast, did not recall seeing Zhao entering the office. He was among about a dozen people queuing inside to sign up for compensation for houses that will be demolished to make way for development.

Li said he was near the back of the line and three people behind his wife when the bomb went off.

'The bomb exploded under an office desk a few meters from me,' Li said. 'Everything in the room seemed to vanish all of a sudden after the explosion.

'My wife was blown away so I called her name. When I found her, she was gasping while looking at me but couldn't speak.' She died before doctors arrived.