Police refused to give any details of the explosion in Peking, which only added to speculation that the cause of the blast could be anything from Uighur Muslim separatists, disgruntled sacked state enterprise workers, to a very public suicide.
The explosion happened at about 5pm inside Zhongshan Park, which flanks the Forbidden City where China's emperors once resided. Across the street is Zhongnanhai, where the country's present-day rulers live and work behind high walls. If it was a suicide, the choice of such a spot would suggest political overtones to the death.
Residents living near Zhongshan Park's west gate confirmed hearing a loud noise at around 5pm. There was one report that a bomb had been placed underneath a park bench. The park gates were closed early, and a police car remained at the entrance throughout the evening. "We are investigating," was all an official at the police station inside the park would say.
China's leaders are especially sensitive to any such events in the run- up to the Hong Kong handover.
It is just over two months since a home-made bomb exploded on a crowded Peking bus, injuring several people and reportedly killing at least two. No-one has yet been arrested for that blast, despite police efforts. It later emerged that there had been two other bombs around that time in Peking, which did not cause serious injuries.
The extreme secrecy of the Chinese authorities, and the lack of any free media, means that information about all these events is scarce. In March, it was assumed that the blasts were probably the work of Muslim separatists from the far western Xinjiang province, because in February three bus bombs in the provincial capital of Urumqi had killed nine people.
But rumours started spreading that at least two of those Peking bombs were the work of angry state enterprise workers who had been laid off from their jobs. Unemployment is soaring in China because over-manned, loss-making state factories are shedding large numbers of workers as they try to restructure to meet the rigours of a market economy. A senior state planner, Wang Dongjin, last week admitted that 54 million state sector employees - a third of the payroll - were probably surplus to requirements.
The Chinese government's obsession with social stability means that it is unlikely to tell the truth about yesterday's bomb. For instance, the police insisted that no-one died in the 7 March bus bomb, but there were independent sources which said there were deaths.
Yesterday, there were reports of two other explosions in China. A blast, presumed to be an accident, injured more than 20 people in a printing factory in the southern city of Zhongshan (coincidentally the same name as the Peking park).
Then a bus explosion near Shunde city, Guangdong province, killed five people. Police said that the explosion was caused by a young couple who died in the blast, although the circumstances were not explained.Reuse content