KHARTOUM, Sudan – A Sudanese court convicted five people Wednesday in the slaying of an American diplomat last year and sentenced four of them to death.

Gunmen firing from a car killed John Granville and his Sudanese driver on Jan. 1, 2008, as he was returning home from a New Year's party in Khartoum, Sudan's capital.

Granville, from Buffalo, New York, worked for the U.S. Agency for International Development. The 33-year-old was working to implement a 2005 peace agreement between Sudan's north and south that ended more than two decades of civil war.

It was the first time an American had been killed in Sudan since 1973, when two diplomats were slain by Palestinian militants.

Four of the defendants were convicted of murder, possession of firearms and other charges and sentenced to death by hanging.

One of them is a former Sudanese army officer who was in active service at the time of Granville's slaying. He was dismissed after he was implicated in the case.

A fifth defendant was convicted of selling the weapons used in the attack and sentenced to two years in prison.

The five men say they were coerced to confess to the American's killing. Their lawyer said he would appeal Wednesday's ruling.

In the attack, a vehicle cut off Granville's car and its occupants opened fire before fleeing. His driver, Abdel-Rahman Abbas, was immediately killed. Granville, who was hit by five bullets, died of his wounds after surgery.

U.S. Secretary of State Hillary Rodham Clinton said in a statement Wednesday that the verdicts are an important step in bringing justice. She said the men were "dedicated to bringing peace and stability to Sudan, and we honor their memory."

The prosecutor in the case said during the trial that the assailants acted out of "religious zeal" and that the group was looking for a Western target during New Year's Eve celebrations.

He said the men attacked Granville after finding that potential targets among places they expected to be crowded or having celebrations were closed or empty.

The shooting came a day after former President George W. Bush signed legislation to allow states and local governments to cut investment ties with Sudan because of the fighting in the western Sudanese region of Darfur, where up to 300,000 people have been killed and 2.7 million displaced.

The chief investigator in the case had testified that the assailants also planned to kill a British diplomat in the country in revenge for a British schoolteacher's decision to let her young students name a toy bear Muhammad, the same name as Islam's founder.

The British diplomat, however, escaped unharmed when he disappeared into a crowd, the police investigator said.

Granville's mother, Jane, said in a statement read out in court that her son's death was a loss for the family and for the people of Sudan.

"His dedication and commitment to supporting and advancing the Comprehensive Peace Agreement guided his efforts toward the dream of a just, stable and peaceful Sudan," the statement said.