BAGHDAD -- Fierce clashes erupted northeast of Fallujah on Saturday between the Iraqi army and Islamic State militants following an ambush the day before that killed a general and staff officers.

Militants launched a complex attack on Friday involving a bulldozer packed with explosives against a convoy as it approached an army camp, killing 1st Division commander Brig. Gen. Hassan Abbas Toufan and three staff officers in the Nadhem al-Taqseem region south of Lake Tharthar.

Ten soldiers also were killed and a dozen wounded in the attack which was against the nearby battalion headquarters as well, said Lt. Gen. Mohammed Khalaf al-Dulaimi of the Anbar operations command.

Residents of Fallujah said that Islamic State militants paraded an officer and three soldiers allegedly captured in the fighting through the streets in a pickup truck on Saturday. They spoke on condition of anonymity for fear of reprisals.

Troops, including tanks, have been rushed to the area and were fighting Saturday in this rural region dotted with small villages.

The fighting came as three suicide car bombs on the other side of the province targeted the remote desert Trebill border crossing with Jordan, killing three Iraqi soldiers and wounding 10, said Brig. Gen. Saad Maan, spokesman for the Iraqi Interior Ministry.

Last year, the Islamic State overran large sections of the country. In recent months, the Iraqi army, backed by the Popular Mobilizations Units of Shiite and Sunni militia fighters, has been gradually retaking territory.

Security forces had been reporting incremental progress this past week, including seizing a key bridge the militants had been using to supply their forces. Some of the 100,000 residents that had fled Ramadi have started to return.

Fallujah has been firmly under control of the militants since it was overrun in January 2014.

In other violence Saturday, a bomb exploded near an outdoor market in Baghdad's southeastern Jisr Diyala suburb, killing four people and wounding 11, police and hospital officials said. They spoke on condition of anonymity because they were not authorized to speak to journalists.

Associated Press writer Sinan Salaheddin contributed to this report.