BAQUBA, Iraq, Jan. 4 (Xinhua) -- Iraqi security forces Thursday killed a prominent leader of Islamic State (IS) group in Iraq's eastern province of Diyala, while Iraqi army started to withdraw from the provincial urban areas, provincial security officials told Xinhua.

Acting on intelligence reports, the Iraqi intelligence killed IS leader of Diyala province, code-named Abu Ayed, during an operation in an area in Himreen Mountain range in north of the provincial capital city Baquba, which is located some 65 km northeast of Baghdad, according to Sadiq al-Husseini, head of the provincial security committee.

"Abu Ayed is considered one of the important targets of the terrorist organization, who has been monitored and tracked in a very precise operation," Husseini said.

Meanwhile, the Iraqi army troops began Thursday to withdraw from Diyala's cities and towns to areas outside the residential areas in accordance with a government decision to transfer the security file to the police forces, according to Awad al-Rubaie, head of security committee of the town of Abu Saida.

"The army fulfilled its withdrawal from Abu Saida, some 25 km northeast of Baquba, after more than ten years," Rubaie told Xinhua.

The move is part of comprehensive plan that would include all the city and town centers in Diyala as well as in other Iraqi provinces," Rubaie said.

The Iraqi army forces will pull out from the cities and towns according to assessment of their internal security situation and after ensuring the presence of alternative forces of the police to deploy, Rubaie added.

Despite repeated military operations in Diyala province, remnants of IS militants were still hiding in rugged areas near the border with Iran in eastern the province, as well as the sprawling areas extending from western part of Diyala to Himreen mountainous area.

Dozens of IS militants fled their former bases in Salahudin province and Hawijah area in west of Kirkuk after the Iraqi forces cleared these areas from the extremist militants during anti-IS offensives in the past few months.

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

However, small groups of IS militants resorted to deserts and rugged areas looking for safe havens but the security forces are hunting them down from time to time.