A U.S. diplomat and his driver were shot and killed while riding in a car in the Sudanese capital of Khartoum Tuesday, the U.S. Embassy said.

The shooting came a day after a joint African-United Nations force took over peacekeeping duties in Sudan's violence-torn Darfur region.

"This afternoon, the American officer succumbed to his injuries and passed away," said Walter Braunohler, the spokesman at the U.S. Embassy in Khartoum.

It was unclear if the attack was targeted or a random crime.

The crime rate is fairly high in Khartoum, although much lower than in some other east African cities. But because of the Darfur crisis, anti-Western and anti-U.S. sentiment also runs high in parts of Sudan.

The joint force that took over peacekeeping duties in Darfur is intended to be the strongest effort yet to solve the world's worst humanitarian crisis. Since the spring of 2003, the conflict has killed more than 200,000 people and driven 2.5 million from their homes.

Sudanese President Omar al-Bashir has long resisted Western demands that he accept a United Nations force, vowing that he would lead a "jihad" against any UN peacekeeper who sets foot in Darfur.

But in June, he accepted a compromise deal for deployment of a "hybrid mission" of mainly African troops.