BAGHDAD, June 1 (Xinhua) -- Three Iraqi civilians were killed by unidentified gunmen in Iraq's eastern province of Diyala on Saturday, while security forces captured four Islamic State (IS) militants in the province, a security source and the Iraqi military intelligence said.

Three civilians were killed by unidentified gunmen in a village near the town of Abu Saida, some 90 km northeast of Baghdad, Ghalib al-Attiyah, spokesman for Diyala's provincial police, told Xinhua.

The security forces launched an investigation into the incident, al-Attiyah said.

Also in the province, a force affiliated with the intelligence service captured four wanted IS militants, including one who was sentenced to death in absentia over carrying out terrorist acts such as killing, displacement, kidnapping, robbery and fighting security forces, the intelligence service said in a statement.

Despite repeated military operations in Diyala, some IS militants are still hiding in some rugged areas near the border with Iran, and in the sprawling areas extending from the western part of the province to the Himreen mountain range in the northern part of the province.

The security situation in Iraq was dramatically improved after Iraqi security forces fully defeated the extremist IS militants across the country late in 2017.

IS remnants, however, have since melted in urban areas or resorted to deserts and rugged areas as safe havens, carrying out frequent guerilla attacks against security forces and civilians.