In the deadliest attack in Iraq in nearly two weeks, a car bomb exploded at about 11am (0800 GMT) on Tuesday in a crowded open market in the northwestern town of Tal Afar, killing 30 Iraqis and wounding 45, said Brigadier Najim Abd Allah, Tal Afar's police chief.

He said all the victims appeared to be civilians since no Iraqi or US forces were in the centre of Tal Afar, which is 420km northwest of Baghdad.

Other attacks 

Attackers also used two car bombs, three roadside bombs and five drive-by shootings and a mortar attack on a used-clothes market in the capital on Tuesday to kill a total of 15 Iraqis and wound 29, police said.

Another attack involved a car bomb that exploded at about noon at an Iraqi army checkpoint in a busy area of western Baghdad on Tuesday, killing eight Iraqi soldiers and one civilian, and wounding 12 soldiers, said police Captain Qasim Husain.

Fifty-seven suspects were
detained in a joint Iraqi-US raid

In Kirkuk, 290km north of Baghdad, a drive-by shooting killed two police officers riding in a cab and their driver, said police Captain Farhad Talabani.

More than 600 Iraqi and US forces also conducted search operations in southern Baghdad early on Tuesday, detaining 57 suspects and killing two, the US military said.

Constitution campaign

The violence came four days ahead of Iraq's key vote on the new draft constitution, which Kurds and the majority Shia largely support and the Sunni Arabs rejects.

Sunnis are campaigning to defeat the charter at the polls, though officials from all sides have been trying to the last minute to decide on changes to the constitution to swing Sunni support.

Across Iraq, groups opposed to the US-led occupation and the new government are demanding that Iraqis boycott the referendum and have killed 388 people in the past 16 days in a series of attacks.
 
On Thursday, the government plans to impose a 6pm to 6am curfew and to limit vehicle traffic across the country to improve security before Saturday's vote.