Iraq's government imposed a one-day curfew on the capital Baghdad today without explanation, ordering all cars and pedestrians off the streets.
The US military said it had arrested a man at the home of the leader of the main Sunni political bloc on suspicion of planning a series of car bomb attacks on the Green Zone, the vast government and diplomatic compound in the city centre.
"Coalition Force personnel detained an individual at the residence of Dr Adnan al-Dulaimi in Baghdad September 29th.
The detained individual is suspected of involvement in the planning of a multi-vehicle suicide operation inside Baghdad's International Zone," the military said in a statement. It said the man may have been linked to al-Qaeda, and the plan might have been intended to use suicide vests to attack the Green Zone.
Dulaimi is the leader of the Iraqi National Accordance front, the largest Sunni political bloc in parliament. As dawn broke, streets in the centre of Baghdad were quiet.
U.S. helicopters periodically flew overhead. The curfew would remain in place until 6am (local time) tomorrow, Prime Minister Nouri al-Maliki's office said in a one-line statement.
The US military did not comment. Outside Baghdad, a car bomb in front of a police colonel's house in the northern oil city of Kirkuk wounded 10 people, police sources said. A roadside bomb in Iskanderiya, 40 km (25 miles) south of Baghdad killed one person and wounded four.
In Washington, where Iraq has become a crucial political issue ahead of a congressional election in November, the U.S. Congress voted to block the Bush administration from building permanent bases in Iraq or taking control of its oil sector. Those provisions were contained in a bill which authorised $70 billion to pay for the wars in Iraq and Afghanistan through the middle of the next fiscal year.
Congress has now approved about $507 billion for the wars, most spent in Iraq where costs are averaging $8 billion a month, according to the Congressional Research Service.