African Union president Jean Ping has said that the United Nations resolution authorising the use of force to protect civilians in war-torn Libya has been "violated."

The Libya UN Resolution 1973 that the Security Council passed in March has "virtually already been violated in spirit and in letter," AU President Jean Ping said in comments earlier this week that were transmitted on public television Thursday.

Acting under the UN mandate to enforce a no-fly zone and protect civilians, NATO jets have bombarded almost daily since late March key units belonging to Colonel Moamer Kadhafi and his forces including his headquarters.

"We hear that (forces) are out to kill the president (Kadhafi) at his home. I don't know if it's true but... if the rumors we hear are true, we are moving towards a complicated direction which will not be easy to resolve," said Ping.

"Morally and ethically speaking, can we participate in a coalition to decide whether to go bomb a member state of the African Union?" he asked.

The African Union, which comprises 53 members, has called for a cease-fire, he added.

Earlier this week NATO bombed official buildings in the Libyan capital Tripoli, significantly damaging Kadhafi's war machine, NATO Secretary General Anders Fogh Rasmussen said Thursday.

The North African country has been the scene of violent clashes between insurgents and government forces since a popular uprising erupted in mid-February, creating a massive humanitarian crisis.