BEIJING (AFP) - Chinese authorities on Saturday denied claims by a Uighur separatist group that it was behind deadly bus bombings in two cities, state media reported. The group, which calls itself the Turkestan Islamic Party, claimed responsibility for a pair of bus blasts that killed two people Monday in southwest China, and said it would target the Beijing Olympics next month. It made the comments in an online video statement transcribed by the Washington-based Intel Center. The separatist group also claimed responsibility for a bus explosion in Shanghai in May that killed three people, according to the centre, which monitors threats by extremists on the Internet. But a public security official in Yunnan province, where Monday's blasts happened, said no evidence had been found linking the explosions with terrorism, according to the official Xinhua news agency. "We have noticed media reports about the claims, but so far no evidence has been found to indicate the explosions were connected with terrorists and their attacks, or with the Beijing Olympics," Xinhua quoted the official as saying. Police in Shanghai also denied the claims, Xinhua said, saying the blast in the city on May 5 had nothing to do with terrorism. "The blast was indeed deliberate but had nothing to do with terrorist attacks," Cheng Jiulong, deputy head of Shanghai police, told Xinhua. In the video statement claiming responsibility for the bus bombings, Commander Seyfullah of the Turkestan Islamic Party warned of more attacks to come. "Through this blessed jihad (holy war) in Yunnan this time, the Turkestan Islamic Party warns China one more time," Seyfullah said in the video dated July 23, according to a transcript from the Intel Centre. "Our aim is to target the most critical points related to the Olympics. We will try to attack Chinese central cities severely using the tactics that have never been employed," he continued.