At least five people have been killed and more than 100 injured when a chlorine gas tanker exploded north of Baghdad.

Many were hospitalised after inhaling the gas fumes released in the blast in Taji, about 20km from the capital.

Five more people were killed and 11 hurt when a car bomb blew up near a petrol station in southern Baghdad.

Police said they were investigating whether the tanker explosion was caused by a bomb or was an accident.

The explosion took place after the driver of the truck parked it in front of a Shia-owned restaurant on the main road from Baghdad to the north of Iraq

Chlorine gas, which is toxic and can irritate the respiratory system, is used for water purification.

The explosion comes after two days of bombings and shootings which left more than 100 people dead and deflated early optimism over a security crackdown in Baghdad.

Tens of thousands of US and Iraqi troops have been deployed as part of a new plan aimed at bringing the country's sectarian violence under control.

US outpost attacked

The US military confirmed late on Monday that two soldiers had been killed in a "co-ordinated attack on a coalition force combat outpost" in Tarmiyah, about 30km north of Baghdad.

The combat outposts have been created in several districts as part of Operation Imposing Law. US troops conduct operations from them rather than returning to military bases.

"Insurgents initiated the attack on the outpost with a suicide vehicle-borne improvised explosive device detonation," a US statement said.

Witnesses and local authorities said at least one car was driven into the concrete outer barriers around the base, a former Iraqi police station, igniting stored fuel before troops came under fire from an armed group.

Mohammed al-Askari, spokesman for Iraq's defence ministry, blamed the attack on al-Qaida in Iraq.

Nine US service members have been reported killed since the beginning of the weekend, six of them on Monday.

PHOTO CAPTION

U.S. soldiers patrol a neighbourhood known as New Baghdad, southeast of Baghdad, February 18, 2007. (Reuters)