RIYADH (Reuters) - A building in southern Saudi Arabia used by United Nations staff to monitor ceasefire violations in Yemen was damaged by rocket fire on Monday.

Saudi-owned Al-Arabiya TV reported that the entrance of the building in Dhahran al-Janoub province, near the Yemeni border, had been hit by Katyusha rockets launched by the Iranian-allied Houthi group who control Yemen's capital, Sanaa.

United Nations special envoy Ismail Ould Cheikh Ahmed did not attribute blame but said it was "especially tragic that this attack took place at a point in time where we are calling for a restoration of the Cessation of Hostilities".

Neither Ould Cheikh Ahmed nor Al-Arabiya made any mention of casualties.

Saudi Arabia and its Gulf Arab allies have carried out thousands of bombing raids in Yemen since March 2015 in a campaign to try to restore the ousted internationally recognized government of President Abd-Rabbu Mansour Hadi.

A 48-hour truce declared by Saudi Arabia in November failed to halt fighting, and a plan to end the war put forward by Ould Cheikh Ahmed was rejected by Hadi's exiled administration.

In his statement, Ould Cheikh Ahmed urged both parties in the conflict to commit to resuming a ceasefire that he said would open space for renewed dialogue.

(Reporting by Katie Paul, Tom Finn and Ned Parker; Editing by Kevin Liffey)