Suspected Al Qaeda bombers stepped up attacks on key transportation arteries, striking a bridge north of the capital Monday a day after shutting the superhighway south of Baghdad with a huge explosion that collapsed an overpass and killed three U.S. soldiers.

The latest attack, a parked truck bomb, blew apart the bridge that carries traffic over the Diyala River in Baqouba, police said on condition they not be identified by name because they feared retribution. There were no casualties, but motorists and truckers now must use a road that runs through Al Qaeda-controlled territory to reach important nearby cities.

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Baqouba is the capital of Diyala province, which is swarming with Al Qaeda fighters. Those militants were driven out of Baghdad by the four-month-old U.S. security operation and out of Anbar province west of the capital by Sunni tribesman who rose up against the terrorist group.

The attacks on the bridges were only the latest in a campaign to deepen turmoil in Iraq, especially on the vital transportation network linking Baghdad to the rest of the country. Such bombings -- especially suicide attacks -- are an Al Qaeda trademark and one of the group's many and ever-shifting tactics against U.S. and Iraqi forces.

Earlier this month, a bomb heavily damaged the Sarhat Bridge, a key crossing 90 miles north of the capital on a major road connecting Baghdad with Irbil, Sulaimaniya and other Kurdish cities.

In March and April, three of Baghdad's 13 bridges over the Tigris River were bombed. The attacks were blamed on Sunni insurgent or Al Qaeda attempts to divide the city's predominantly Shiite east bank from the mostly Sunni western side of the river.

The most serious attack, an April 12 suicide truck bombing, collapsed the landmark Sarafiyah bridge and sent cars plunging into the brown waters of the Tigris. Eleven people were killed.

U.S. forces used bulldozers Monday to push aside the rubble of the overpass that crashed onto Iraq's main north-south highway just east of Mahmoudiyah, a dangerous triangle of death city with a large Al Qaeda presence.

The suicide truck bombing 20 miles south of Baghdad not only brought down a section of the bridge, it killed three U.S. soldiers at a checkpoint and wounded six other American soldiers along with an Iraqi interpreter, the U.S. military said in a statement issued at its Camp Victory headquarters at Baghdad International Airport.

Tumult arose in Iraq's fragile political structure Monday when lawmakers declared themselves fed up with the parliament speaker and voted to oust the controversial Sunni politician from his powerful post.

Mahmoud al-Mashhadani is a physician who was jailed by Saddam Hussein and who had said from the parliament speaker's chair that those who attack American forces should be treated as heroes. He was voted out in a closed session of the Shiite-dominated 275-member legislature.

His ouster appeared to have grown out of a shouting match Sunday with lawmaker Firyad Mohammed Omar, a Shiite Turkoman.

Omar had complained to the speaker about the heavy-handedness of al-Mashhadani's bodyguards; al-Mashhadani responded abusively, according to lawmakers who spoke on condition of anonymity because of the sensitivity of the issue. Omar told fellow legislators that the speaker's guards had assaulted him.

Al-Mashhadani's deputy, Khaled al-Attiyah, who chaired the closed session, will assume the duties of the speaker until a replacement is chosen.

"It's an illegal decision made by a juvenile house," al-Mashhadani told the U.S.-funded Radio Sawa in an interview posted on the Internet.

Al-Mashhadani is part of the Accordance Front, parliament's largest Sunni Arab bloc with 44 of the house's 275 seats. Salim Abdullah, a fellow lawmaker from the Accordance Front, said it would offer a replacement for al-Mashhadani within a week.

The speaker's job is allotted to a Sunni member of parliament according to an agreement among lawmakers who struggled for months to chose their leadership, a prime minister and government.

"We agreed to replace him because we want to improve the house's performance," Abdullah told The Associated Press.

But al-Mashhadani told Radio Sawa that if his performance as speaker were below par, Shiite Prime Minister Nouri al-Maliki's was "much worse." The level of competence of President Jalal Talabani, a Sunni Kurd, was "even worse because he does nothing," the former speaker said.

The man expected to become Britain's next prime minister, meanwhile, met with Iraqi leaders in an unannounced visit. Treasury chief Gordon Brown has vowed to study his country's participation in the Iraq war in the face of growing opposition at home.

Brown, slated to succeed Tony Blair this month, was on a one-day fact-finding mission, British officials said.

In London, the House of Commons rejected a motion by Britain's opposition Conservative Party calling for a formal inquiry into the decision to go to war in Iraq. By a vote of 288 to 253, the lower house of parliament sided with Blair, who has ruled out such an inquiry while British troops are deployed in Iraq.

Like so much in Iraq these days, even final exams for high school seniors aren't going as planned: Iraq's Education Ministry delayed the start of finals after some of the test questions were leaked to students, an official said.

A week of final exams had been due to start Tuesday with the Islamic education test, but that was put off until July 1 while authorities investigate reports of cheating, an official said, on condition of anonymity because of the sensitivity of the subject.

Iraqi police, morgue and hospital officials reported 34 deaths in sectarian violence across Iraq on Monday, including 17 bodies dumped on Baghdad streets and believed to be the victims of Shiite death squads.