The US-led coalition, meanwhile, said it had anticipated the wave of bombings on the Shia holiday of Ashura and arrested several al-Qaeda members ahead of the carnage.

The measures came amid criticism from Shia Muslim leaders that the US-led Coalition Provisional Authority was not doing enough to protect civilians, as the Jordanian Abu Mussab al-Zarqawi and al-Qaeda emerged as prime suspects.

"The US has committed 60 million dollars to support border security," the top US official in Iraq, Paul Bremer, said late Wednesday. "We are adding hundreds of vehicles and doubling border police staffing in selected areas."

Around 170 people were killed and more than 500 wounded in Tuesday's bombings in the Shia holy city of Karbala and at a Baghdad mosque, the worst attacks in Iraq since the fall of former dictator Saddam Hussein last April.

"All indicators are that the Zarqawi network was involved in these attacks, how large, we don't know the size of it, we presume it to be well funded," a senior coalition official said Thursday.

Bremer said the aim of Zarqawi, who has been firmly linked to other bombings in Iraq, was to provoke sectarian violence between the majority Shia and the smaller Sunni Muslim communities.

"Zarqawi and like-minded terrorists are in a losing race against time," he said.

In Karbala, where a suicide bomber, bombs planted in pushcarts and mortars fired from afar killed around 100 people, a Polish coalition spokesman said seven suspected al-Qaeda members were arrested well before the attacks.

Polish spokesman Warrant Officer Zbigniew Dabkiewicz, told AFP that a raid on February 25 which netted nine men and large quantities of narcotics and weapons had actually exposed part of the al-Qaeda network operating in the province.

"Two of the men were from the al-Qaeda group connected with Zarqawi," he said. "That's confirmed."

He described Osama bin Laden's network as the best-organised threat in the Polish-controlled provinces of Babil and Karbala.