UN Secretary General Ban Ki-moon expressed concern on Monday over the deterioration of the situation in Sudan's Darfur region following a string of attacks against peacekeeping troops there. Two police advisers of the joint UN-African Union peacekeeping mission in Darfur (UNAMID) were kidnapped on Saturday. Other similar incidents, including military ambushes of UN convoys, have taken place in recent months, dpa reported. "Continued attacks on UNAMID peacekeepers and abductions and mistreatment of UN staff and humanitarian workers will only aggravate the situation," Ban said in a statement. Ban urged the Sudanese government to apprehend the kidnappers and attackers of UN troops and to take all measures to assist and give access to relief workers trying to help needy Darfurians. The UN-AU peace force was deployed to try to maintain peace and security in troubled Darfur, where the war between Sudanese government troops and African rebel groups has been going since 2003. More than 300,000 people have been killed and 2.7 million people became refugees.