A explosion ripped through a street in the centre of the Kenyan capital Nairobi on Sunday, injuring dozens of people and sending ambulances and police rushing to the scene, an AFP photographer said. Prime Minister Raila Odinga visited the scene of the blast and said in a brief statement to reporters that at least 28 people had been injured. The strong explosion damaged cars and buildings along a street packed with auto parts sellers and garages on the city\'s Kiniryaga Road, the photographer said. A pall of black smoke rose from a petrol station which had been damaged in the blast. Officials declined to say if the blast was accidental or the result of a bomb. In December, three people were killed in December in a grenade attack on a bus from the Ugandan capital Kampala, which police blamed on the Somali Islamist Shebab group. The attack happened a few hundred metres from the site of Sunday\'s explosion. The Shebab, which controls vast swathes of neighbouring Somalia, has threatened to attack Kenya over its support for the fragile UN-backed transitional government in Mogadishu.