Islamic State militants ambushed an Iraqi army convoy Friday with a bulldozer packed with explosives, killing the commander of the Iraqi 1st Division and three of his officers north of Fallujah, military officials said.

The suicide bomber attacked the convoy of Humvees and then militants opened fire killing Brig. Gen. Hassan Abbas Toufan, colonel and two lieutenant colonels in the Nadhem al-Taqseem region, said a a member of the division of an intelligence officer. The number of soldiers killed was not released.

The attack represents a setback for the Iraqi army, which is embroiled in a fierce battle to reconquer western Anbar province, which has been under the control of ISIS for the last year. Fighting has been focused on the provincial capital of Ramadi, were the government had been making slow progress.

Earlier on Friday, the army had recaptured the important al-Houz bridge over the Euphrates in western Ramadi, which had served as a primary supply route for the militants, according to police Col. Mahdi Abbas.

The security situation in Ramadi sharply deteriorated after the IS group seized three villages around the city, forcing an estimated 100,000 to flee their homes. Many had just started to return in the past few days as Iraqi soldiers and police have been able to secure the center of Ramadi and push the militants back from some areas of the city.

During weekly Friday prayer, Iraq’s most revered Shiite cleric, Grand Ayatollah Ali al-Sistani urged the country’s politicians to end all disputes in order to confront challenges Iraq faces.

"It is important that the brothers (the politicians) should come out with final and drastic solutions for the problems," said al-Sistani's representative during a sermon Friday in the holy Shiite city of Karbala.

Many Iraqis blame the rivalries among the country’s political leadership for the humiliating defeat suffered by government forces in the last year at the hands of ISIS.

In Friday's violence, police officials said a bomb exploded near an outdoor market in the Sunni town of Tarmiyah, north of Baghdad, killing four people and wounding eight.

A bomb near a courthouse killed three people and wounded nine in the town of Mahmoudiyah, south of Baghdad.

Medical officials confirmed the death toll. All officials spoke on condition of anonymity because they are not authorized to speak to the media.

No group immediately claimed responsibility for the attacks.

The Associated Press contributed to this report