Iraq attack kills three US troops

Three US soldiers have been killed and two wounded in a rocket attack on a combat outpost in the southern Iraqi city of Nasiriya, the US military says.

An Iraqi civilian was also injured in the early morning "indirect fire incident" at the base, 320km (200 miles) south-east of Baghdad, it added.

Twelve US troops and an interpreter have been killed in Iraq since Monday.

The deaths come a day after a roadside bomb hit a bus near Nasiriya, killing 16 people according to Iraqi officials.

The attack was the deadliest on a day in which at least 44 people were killed, unsettling the relative calm which has existed in much of Iraq since the US troop surge.

RECENT US TROOP DEATHS 10 March: Eight killed by bombs in Baghdad and Diwaniya 9 February: Four killed by roadside bomb near Baghdad 28 January: Five killed by roadside bomb in Mosul 9 January: Six killed entering a booby-trapped house north-east of Baghdad

On Monday, five US soldiers were killed by a suicide bomber while on patrol in Baghdad. Three others died in a roadside bombing in Diyala province.

Another soldier was killed on Tuesday after his patrol was hit by a roadside bomb near Diwaniya, south of Baghdad.

Meanwhile, a new survey suggested that only a minority of Americans know how many US soldiers have died in Iraq since the invasion five years ago.

Just 28% gave the correct casualty figure of nearly 4,000, according to the Pew Research Center. In August last year, 54% answered correctly, it said.