An official of the Patriotic Union of Kurdistan was also killed and another US soldier was injured in the drive-by attack in the northern city of Mosul on Wednesday.

 "We had two vehicles drive by and shoot at two sides of the street. They fired on the PUK (Patriotic Union of Kurdistan) offices and they fired on the gas station and then they sped off," said Major Trey Cate, spokesman for the 101st Airborne Division in Mosul.

A Kurdish leader in Mosul told AFP one his officials had died from the gunmen's fire as he drove out of the office.

Cate had earlier said a gunman had been shot dead in the attack on a gas station patrolled by US troops on the city's east side of the Tigris river.

Also on Wednesday Iraq stepped up efforts to deal with a shortage of fuel in this country with the world's second-largest oil reserves, the oil ministry said.

"Each driver can have only 50 litres, not more, at the price of 20 dinars (one US cent) each litre," Asem Jihad, the spokesman for Iraq's oil ministry, told AFP.

He also said gas station operators who sell to the black market will face lengthy jail terms under a new law effective from Wednesday.

Motorists say the gas station queues, some as long as three kilometres (two miles) have become increasingly common since the end of the Muslim holy month of Ramadan in late November.