UN Secretary-General Kofi Annan condemned on Tuesday the two shooting attacks on African Union monitors in Sudan's war-torn Darfur region and called for respect of the observers' neutrality.

A statement issued by Annan's spokesman said the UN leader shared the AU's "serious concern" about the shooting at two African monitors on Monday in South Darfur.

The first incident occurred in an area south of Nyala, where AU monitors were investigating an attack on a village. The second occurred near Shangil Tobai, where another team was investigating reports that government air bombings had taken place last week. No casualties have been confirmed in either incident.

Annan "strongly condemns this attack, which could jeopardize the fulfillment of the African Union mission in Darfur and which occurred at a time when the military observers were conducting investigations to verify allegations of aerial bombardments and other violations of the N'Djamena ceasefire agreement," the statement said.

The truce accord was signed last year in the Chadian capital of N'Djamena to halt fighting and allow access by aid groups.

"He calls upon the government and rebel forces in Darfur to respect the neutrality of African Union monitors, observers and police, as well as all international humanitarian workers, and to guarantee that they operate in the region under conditions of safety and security," the statement added.

Annan also urged all parties to investigate the shooting incident and take immediate action against those found responsible.

Darfur has been mired in a civil war since February 2003. The African Union currently has some 1,000 monitors in the region to oversee the ceasefire.