Iraq's higher education minister escaped unharmed Wednesday from a car bomb attack on his convoy that lightly wounded three of his bodyguards, a ministry spokesman said.

The attack on independent Shiite lawmaker Sami al-Mudafar was the second attempt on his life in the past two years. The first occurred when he was education minister under the transitional government of former Prime Minister Ayad Allawi.

Higher Education Ministry spokesman Bassel al-Khatib said a car bomb exploded in downtown Baghdad's Karradah district as al-Mudafar's four-vehicle convoy passed. Al-Khatib could not say if the car was driven by a suicide attacker or if the bomb was detonated by remote control.

Security has been heightened across Iraq for the Shiite festival Ashoura, which reaches its climax Thursday. The celebrations, which mark the seventh century death of revered Shiite saint Imam Hussein, have been targeted in the past two years by Sunni Arab bombers who have killed more than 230 people.

Interior Ministry spokesman Brig. Adnan Abdul-Rahman said extra security forces will be stationed along the main roads linking Baghdad to the holy southern cities of Karbala and Najaf, where hundreds of thousands are expected to attend Ashoura festivals.

The government also announced the closure of northern Baghdad's al-Aima Bridge, which links the Shiite neighborhood of Kazimiyah to the predominantly Sunni area of Azamiyah. Last August, at least 1,000 Shiite pilgrims celebrating a different festival were killed in a stampede on that bridge caused by somebody claiming there was a homicide bomber in their midst.

Thousands of security forces have been frisking people and checking cars at Ashoura pilgrimage sites in a bid to prevent a repeat of the violence that has marred previous commemorations, at which Shiite pilgrims beat and whip themselves in a blood-soaked display of mourning over Imam Hussein's death.

Ten roadside bombs were defused near a bridge in Latifiyah, about 20 miles south of Baghdad, that police believed were set to target Shiite visitors heading to Karbala, Babil police said.

Police also found the bodies of another four Shiite pilgrims who had been shot repeatedly and dumped on Baghdad's northern outskirts. Police also said they found the bodies of three men blindfolded, bound and shot in eastern Baghdad's Sadr City.

The motive for the bomb attack on the minister was not immediately clear, but al-Mudafar has been reportedly outspoken against increasing the influence of Islam on university campuses. Sunni Arab insurgents have also repeatedly targeted members of the U.S.-backed Iraqi government.

Al-Mudafar, a lawmaker in the outgoing parliament, did not run in Dec. 15 elections for the next four-year parliament.

Under Saddam Hussein's regime, al-Mudafar was a biochemistry professor at University of Baghdad college of sciences and was elected head of the university following the 2003 U.S.-led invasion of Iraq.

Separately Wednesday, a roadside bomb in eastern Baghdad missed a U.S. convoy but killed an Iraqi passer-by and wounded another, while a second blast injured two Iraqi policemen in northern Baghdad, police said.

Police said they have arrested two teenage brothers suspected in the killing of a Sunni Arab community leader who headed the city council in the former extremist stronghold of Fallujah.

Lt. Taha Mohammed said the brothers were detained Tuesday after Sheik Kamal Nazal, a Sunni preacher and chairman of the Fallujah city council, was shot dead by gunmen in two cars as he walked to work.

Mohammed said the brothers have since been handed over to U.S. forces in Fallujah for questioning. No comment was immediately available from the American military.

No group claimed responsibility for the killing, which occurred in one of the most tightly controlled cities in Iraq. However, it appeared part of a campaign of intimidation by Sunni insurgents against Sunni Arabs interested in promoting a political settlement to stem the violence in the country.

An unarmed and unmanned U.S. aircraft providing security coverage for Ashoura went down near Baghdad's eastern Sadr City neighborhood Tuesday, but the cause of the mishap was not immediately known, the military said Wednesday.

Air traffic controllers lost contact with the aircraft shortly after it took off at about 10:30 a.m. from an airfield in Taji, 10 miles north of Baghdad, the military said. The aircraft, belonging to Multi-National Division-Baghdad forces, made a "controlled parachute landing," said the military.