A policeman was killed and another injured in a roadside bomb explosion near a police patrol in the town of Baladruz, some 30 km east of capital city of Baquba, the source told Xinhua on condition of anonymity.

In separate incident, four policemen and four civilians were wounded when a roadside bomb detonate near a passing police patrol in the Gatoon area near Baquba, some 65 km northeast of Baghdad, the source said.

Two of the wounded policemen were in critical conditions, the source added.

Also in the province, the source said that a police commando force raided a house in the town of Khalis, 15 km north of Baquba, and released two kidnapped people, he said.

The troops also detained one of the kidnappers during the raid which was based on intelligence reports, he added.

A day before, Khalis was the scene of a bike bomb explosion at a busy area near a Husseiniyah, or a Shiite mosque, killing three people and wounding some 20 others.

Diyala province, which stretches from eastern edges of Baghdad to the Iranian border, has been the stronghold of al-Qaida in Iraq network and other insurgent groups since the U.S.-led invasion in 2003.