Syria's interior minister said an explosion near a bus parked at a gas station was an accident and three people were killed. Witnesses said the blast, in the Damascus suburb of Sayyida Zainab, targeted a busload of Iranian pilgrims causing an unconfirmed number of casualties. Said Mohammad Sammour ruled out a terrorist attack in a statement to state-run Syrian TV. He said the bus driver and two gas station workers were killed when a tire they were pumping air into exploded. Syrian TV quoted Sammour as saying "there were no explosives involved" in Thursday's accident. However, Iranian diplomats, speaking on condition of anonymity because they were not authorized to speak to the media, said two Iranians and four Syrians were wounded by the explosion. The suburb is popular with Iranian and other Shi'ite pilgrims and is the location of a shrine dedicated to the granddaughter of the Prophet Muhammad. A private Syrian television station, Ad-Dounial TV, said six people were killed in the blast. Iranian state television also reported six killed, including two Iranian bus drivers. It said the explosion occurred while the bus was fueling up at a gas station near the shrine. Police sealed off the area and reporters were banned from reaching the site of the explosion. There was no way to independently confirm the casualty figures. The blast coincided with a visit to Syria by Iran's nuclear negotiator Saeed Jalili, who was in Damascus for talks with Syrian officials about Iran's controversial nuclear program. Syria's state-run media did not report the blast. Bomb attacks are rare in Syria, where the regime tightly controls the country and cracks down on any form of dissent. In September 2008, a suicide bomber detonated his car near a Syrian security complex on the southern outskirts of the capital, killing 17 people. It was the biggest and deadliest attack in the country since the 1980s when the government fought an uprising by Muslim militants. In September 2006, Islamic militants tried to storm the US Embassy in Damascus in an unusually bold attack in which three assailants and a Syrian guard were killed. The Syrian government blamed the attack on an al-Qaida-linked group called Jund al-Sham, or Soldiers of Syria.