UN Secretary-General Ban Ki-moon on Monday called for restraint in the contested Abyei region of Sudan.

"The secretary-general is deeply concerned by the continued tension and violence in the Abyei area," said a statement issued by Ban's spokesperson.

"He calls upon the leadership of the National Congress Party ( NCP) and Sudan People's Liberation Movement (SPLM) to restrain the local communities in Abyei and to implement the short-term containment measures as agreed in the Kadugli agreements."

A referendum to determine whether Abyei would join the north or south of Sudan was due to be held in January in conjunction with the vote on southern Sudanese secession that took place. A voting commission for Abyei, however, failed to form due to local communities' disagreements over voting rights, and the region continues to be disputed.

The statement read that Ban would like talks on Abyei to be resumed and completed "as a matter of priority."

In response to tensions, the UN Mission in Sudan (UNMIS) has increased its patrol activities on the ground, and is attempting to reduce tensions through engaging various parties, said the statement.

"The Secretary-General deplores, however, that the mission has been consistently refused access to areas of conflict and considerably restricted in its movement, and appeals to both parties to allow unhindered access to these areas in order to assess the situation and immediate needs on the ground," the statement said.