Three car bombs exploded in Baghdad on Tuesday, killing at least five people, police said.
A car bomb targeting a US military convoy exploded on a road about 500 metres from the main avenue leading to Baghdad's international airport, police Captain Thamir Talib said.
Four civilians were killed and seven were wounded, including two police officers, he said.
In a separate incident, sources at Iraq's interim Interior Ministry said, four people were wounded when a car bomb targeting an Iraqi army convoy went off on Tuesday morning in the vicinity of Bab al-Muadham district in central Baghdad.
Another car bomb exploded in northeastern Baghdad, killing one child and wounding at least four people, including a police officer, police Colonel Muhannad Sadun said. The explosion rocked the Amal neighbourhood about 9km from the airport.
The bomber was trying to hit a traffic police patrol but crashed into a tree, Sadun said.
Attacks on US patrols in Iraq
show no signs of tapering off
In a report unconfirmed by US officials, witnesses said some US troops were also wounded in the blast.
When US forces arrived on the scene to evacuate them, another car bomb exploded, wounding more troops.
One Humvee was destroyed and two civilian cars were in flames, witnesses said.
A US military spokesman said he was checking into the report.
On Monday, a Marine assigned to I Marine Expeditionary Force was killed in action while conducting security and stability operations in Anbar province.
The US military said it was withholding identification until the family was informed.
On Tuesday, an unknown group of fighters shot at two US marine helicopters near the Syrian border in Iraq and damaged one of them, before the aircraft destroyed the fighters' pick-up truck, the US military said.
A UHN-1 Huey and an AH-1W Cobra received machine-gun fire from the back of the truck near the border town of al-Qaim, a marine spokesman said in a statement.
"Both aircraft engaged the target with rocket and machine-gun fire. The pickup was destroyed. We can't confirm at this time the condition of the enemy," the statement read.
US helicopters frequently draw
fire from fighters on the ground
"There was very minor damage to the Huey, and no casualties."
In a separate development, authorities in Najaf, south of Baghdad, have arrested a suspect believed to have been involved in the assassination of Shia leader Ayat Allah Muhammad Baqir al-Hakim, Najaf police chief Major-General Ghalib al-Jaziri said.
He added that Ramzi Hashim was arrested 10 days ago and confessed during investigations that he was one of the assailants who carried out the 29 August 2003 attack outside a mosque in Najaf that killed more than 85 people, including al-Hakim.
The Baghdad office of Abd al-Aziz al-Hakim, the cleric's younger brother and leader of the United Iraqi Alliance, confirmed that a suspect involved in the assassination of
the senior cleric was detained in Najaf more than a week ago.
Al-Jaziri said Hashim came to Najaf along with other accomplices to carry out attacks on the office of Iraq's top Shia authority, Grand Ayat Allah Ali al-Sistani.
Attacks on the oil infrastructure
have increased in recent months
Aljazeera has further learned that US forces and the Iraqi army have arrested a number of people in the neighbourhood of Abu Ghraib in western Baghdad.
The campaign to arrest suspects that started at dawn on Tuesday is continuing.
Also on Tuesday, an unknown group of fighters blew up an oil pipeline near the northern city of Kirkuk, an Iraqi army officer said.
"A pipeline route between the Kirkuk oil fields and the Baiji refinery caught on fire at 2.30pm (1130 GMT) the result of saboteurs," Captain Ala Abd Allah, whose men are charged with guarding Iraq's oil infrastructure, said.
Abd Allah, part of a 3000-strong oil-protection force, said firemen hoped to control the blaze by Wednesday and put it out in three days.
In recent months, fighters have intensified their attacks on Iraq's oil infrastructure, targeting crucial pipeline sections and convoys carrying fuel.
Members of parliament will take
the oath of office on Wednesday
Kirkuk's vital pipeline to the Turkish Mediterranean port of Ceyhan has been shut down for most of the past two years, at first because of the US-led invasion of Iraq and later due to incessant attacks.
Amid this backdrop of ongoing violence, a statement issued on behalf of the yet-to-convene parliament said that 275 newly elected members would take the oath of office on Wednesday.
They will then elect a parliament speaker and two deputies, as well as the new transitional government's three-member Presidency Council - consisting of the president and two vice-presidents.
The United Iraqi Alliance has proposed Shaikh Fawaz al-Jarba, one of the few Sunni Arabs in its coalition, to be speaker. It was unclear if he would be acceptable to the Sunni community.
The Shia alliance won 140 seats in the National Assembly, but need the Kurds' 75 seats to assemble the two-thirds majority required to elect a president, who will then nominate the prime minister.