The joint U.N.-African Union mission in Darfur says a Ugandan member of the force has been fatally shot.

The police officer is the first member of the mission slain since the troops deployed five months ago.

The officer, John Kennedy Okecha, was found dead in a vehicle operated by the UNAMID force in North Darfur on Wednesday, the mission said. He had been shot three times, in the neck, chest and stomach.

UNAMID described the killing as "an act of cold blooded murder" and appealed to anyone with knowledge of the slaying to come forward.

It said Kennedy was killed on the outskirts of Zam Zam, a large refugee camp with some 40,000 refugees about 3 miles from El Fasher, the capital of North Darfur state.

"I learned of this wanton and barbaric act with disbelief and dismay. This was a hideous and callous crime against an unarmed peacekeeper and I condemn it without reservation," said Henry Anyidoho, deputy joint special representative of UNAMID.

UNAMID began deploying in war-ravaged Darfur in December after difficult and protracted negotiations to get Sudan to agree to the new peacekeeping force. It replaced an under-equipped and ineffectual AU force of 7,000.

But the new joint force only has about 7,500 troops and fewer than 2,000 police on the ground, although a total of 26,000 have been authorized.

Last week, dozens of men on horseback armed with machine guns and rocket-propelled grenades ambushed Nigerian peacekeepers with UNAMID in West Darfur state, though no casualties were reported.

U.N. peacekeeping chief Jean-Marie Guehenno warned earlier this month of an alarming increase in violence in the Darfur region in western Sudan which spread recently to the capital Khartoum and said it could escalate further.

At U.N. headquarters in New York, Guehenno said Thursday that the Darfur force is still inadequate.

"Do we have enough resources to protect ourselves and therefore to protect the people we have come to help? Frankly, as I've told you before, we don't have them in Darfur," he said. "We don't have the firepower that would allow us to do what we're expected to do. And that's very dangerous. It's dangerous for our people."

He said the U.N. had just put up a memorial at its headquarters to all the peacekeepers who have been killed around the world, "and you see with this tragic death yesterday, that memorial is already out of date."

Guehenno said he had spoken to the force commander of Darfur peacekeepers and explained they were in a difficult position.

"If you hunker down, you lose the trust of the population, which wants you to be all over the place patrolling and making a difference. If you move around but you do not have enough resources, you may be victim to the kind of incidents that have happened in the last few days," he said.

Ethnic Africans in Darfur took up arms against the Arab-dominated government in Khartoum in 2003 to fight discrimination. The U.N. says 2.5 million people have been forced from their homes during the five-year conflict — including 150,000 since the beginning of the year. It says the death toll could be 300,000.