Four United Nations peacekeepers serving in Sudan's troubled Abyei area were killed today and seven others were injured after a landmine detonated during a patrol, the UN reported.

The Ethiopian blue helmets, part of the UN Interim Security Force for Abyei (UNISFA), were on patrol in Mabok, southeast of the town of Abyei, when they were killed.

In a statement issued by his spokesperson, Secretary-General Ban Ki-moon voiced sadness at the deaths.

"The Secretary-General expresses his deepest condolences to the families, friends and colleagues of those killed, as well as to the Government of Ethiopia," the statement noted. "He also expresses his concern for the well-being of the seven other peacekeepers who were injured in the explosion."

More than 500 troops, all Ethiopian, have been deployed since the Security Council voted in June to establish UNISFA after north-south violence in Abyei and surrounding areas forced more than 100,000 people to flee their homes.