BEIJING - CHINA said on Tuesday that a probe into two deadly bus explosions had not turned up any evidence that they were terrorist attacks linked to next month's Beijing Olympics.

Police have said two people died on Monday in the blasts aboard two public buses in Kunming, 2,100 kilometres southwest of Beijing, calling the explosions deliberate acts of 'sabotage.' 'We have not found evidence of a link to the Olympics but we will continue to make efforts to find out the truth,' foreign ministy spokesman Liu Jianchao said, providing no other details.

Mr Liu was asked whether police had found any evidence that terrorist groups were behind the explosions and whether there was any connection to the Olympics.

However rights groups have accused the government of exaggerating or fabricating the threat as an excuse to silence dissent in Xinjiang, where many members of the Uighur ethnic minority complain about repressive Chinese rule.

Kunming, the capital of mountainous Yunnan province bordering Myanmar, remained tense on Tuesday, state media reported, with authorities yet to explain who was behind the blasts.

However, the China Daily said investigators had found that ammonium nitrate, a chemical compound that they said was generally used by the military, was used in the blasts.

Police have beefed up security at airports and highways in Kunming, it said.

The explosions have come at the worst possible time for Chinese authorities as they strive to stress their preparedness against possible terror attacks targeting the August 8-24 Olympic Games in Beijing.

Fourteen people were also injured in the blasts, including a woman who sustained life-threatening injuries.