Four suicide bombers blew themselves up in Iraq on Saturday, killing at least six people, as Shiite Muslim (search) worshippers around the country celebrated the holiest day of the year, one day after at least 36 people were killed in a string of attacks.

Saturday's bombings, during the religious festival of Ashoura, came despite stepped-up security around the country. Authorities had hoped to prevent a repeat of last year's attacks during Ashoura in which insurgents killed at least 181 people in twin blasts in Karbala and Baghdad (search).

On Saturday, a suicide bomber walked into a tent outside a Sunni mosque in western Baghdad and blew himself up, killing at least three people and injuring 10, police captain Hussain al-Ani said. About 50 people were inside the tent attending a funeral.

It was unclear why the attacker blew himself up inside a tent full of Sunnis, set up outside the Fatah Pasha mosque, but similar structures were set up outside Shiite mosques for the Ashoura celebration. Most attacks by insurgents — who are thought to be predominantly Sunni extremists — are aimed at Shiites.

Another suicide bomber who tried to kill a group Iraqi National Guard troops near a mosque in northwest Baghdad on Saturday detonated prematurely and killed only himself.

A third bomber blew up a car outside an Iraqi National Guard (search) base in Baqouba, 35 miles northeast of Baghdad, killing one Iraqi guardsman and wounding another, police Col. Muthafar Shahab said. The suicide bomber also died in the blast, he said.

A fourth suicide bomber blew up his car at an Iraqi army checkpoint in Latifiya, 20 miles south of the capital, killing two Iraqi soldiers, an army officer said on condition of anonymity.