BAGHDAD – A bomb-rigged truck exploded at a checkpoint Tuesday near the western city of Ramadi, killing two U.S. Marines and wounding three others in an apparent strike by al-Qaida in Iraq in one of its former strongholds.

At least one civilian also died and two dozen were injured in the blast, the latest in a string of recent strikes in areas where local Sunnis have joined U.S. forces to battle al-Qaida.

Ramadi is the capital of Anbar province, which was once held by insurgents. But it has been relatively peaceful since local Sunni tribal leaders joined forces with the U.S. military against the terror movement.

Iraqi police said the suicide attacker drove a small water tanker packed with explosives to the checkpoint and detonated them when he reached the guards. The U.S. military said two Marines were killed and three injured.

In Diyala province, north of Baghdad, a woman detonated an explosive vest at the entrance to an Iraqi police station in Jalawla, killing eight policemen and a Kurdish security guard, police said. Ten other people were wounded.

It was the second suicide attack by a woman in as many days in Diyala, which has been a flashpoint in the battle against al-Qaida. A young woman blew up herself Monday at the headquarters of a group of U.S.-allied Sunni fighters, killing three people and wounding three others, the U.S. military said.

Al-Qaida has been regrouping after suffering a devastating blow last year when thousands of Sunni tribesmen turned against them. Last weekend, al-Qaida announced a one-month offensive against U.S. troops and Sunnis who have joined forces with Americans.

Osama bin Laden’s deputy, Ayman al-Zawahri, said in an audiotape posted Tuesday on the Internet that al-Qaida-led insurgents in Iraq were the “primary force” in battling the Americans and “challenging Iranian ambitions” in this country.

Attention has focused on crackdown against Shiite militias.