BAGHDAD, Dec. 23 (Xinhua) -- Four people were killed Monday when a bomb left by the Islamic State (IS) group exploded in the central province of Salahudin, said a provincial police officer.

The explosion occurred in an agricultural area north of the provincial capital, Tikrit, some 170 km north of Baghdad, according to Mohammed al-Bazi from the Salahudin police command media office.

The security situation in Iraq has improved since the defeat of the IS in 2017. However, IS remnants have sneaked into urban centers, deserts, and rugged areas, carrying out frequent guerrilla attacks against security forces and civilians. ■