TIKRIT, Iraq, June 22 (Xinhua) -- An army officer and two soldiers were killed Friday in a tunnel bomb explosion in Iraq's central province of Salahudin, a local security source said.

The incident occurred during an operation by the joint army and police forces to clear areas from Islamic State (IS) militants in the west of Shirqat city, some 280 km north of the capital Baghdad, Maj. Saadoun al-Jumaili from media office of the provincial operations command, told Xinhua.

The troops destroyed several IS tunnels and hideouts during the operation, but one of the tunnels was apparently booby-trapped and detonated while the troops were searching it, killing three security personnel, and wounding two soldiers, Jumaili said.

He said the troops will continue the mission in the vast rugged area in Salahudin that extends to the provincial borders with Nineveh and Anbar.

During the past months, hundreds of IS militants fled their former urban strongholds in Mosul, Salahudin Province, and Hawija area in the west of Kirkuk, after Iraqi forces cleared these regions during major offensives.

On Dec. 9, 2017, Iraqi Prime Minister Haider al-Abadi officially declared full liberation of Iraq from the IS after Iraqi forces recaptured all the areas once seized by the extremist group.

However, small groups and individuals of IS militants have since then regrouped in rugged areas, including Himreen, carrying out attacks against security forces and civilians despite operations from time to time to hunt them down.