In the attack on the petrol station, three car bombs detonated one after the other in southwest Baghdad.
The explosions occurred at 9:45am in Biyaa, a mixed Sunni Arab and Shia section of the city.
The patchwork of Sunni and Shia neighbourhoods in southwest Baghdad is a frequent site of clashes between rival armed gangs.
The attack in the Biyaa area is the latest in a number of multiple car bomb attacks in the Iraqi capital, including the bloodiest bombing since the US invasion two weeks ago which killed more than 200 people.
Onus on Washington
The attacks come a day after Abdul Aziz al-Hakim, a cleric and head of the biggest party in Iraq's government, SCIRI, met George Bush in Washington.
Hakim, a former leader of his party's armed militia wing, denied accusations that Shias were stoking sectarian violence in Iraq. He put the onus on Washington to take tougher action against fighters.
"The strikes they are getting from the multinational forces are not hard enough to put an end to their acts," he said.
"Eliminating the danger of civil war in Iraq could only be achieved through directing decisive strikes against Baathist terrorists (and other Islamists) in Iraq."
"Otherwise we'll continue to witness massacres," he said in a speech after meeting Bush.
Hakim rejected any international or regional interference that exceeds the political process in Iraq. He also called on the US not to pull out its forces from Iraq.
The US president said he and Hakim had discussed a need for Iraqi leaders to "reject the extremists that are trying to stop the advance of this young democracy".