John Granville was killed while driving home on New Year's Day

Four men in Sudan have been sentenced to death for the killing of a US diplomat and his driver last year.

John Granville and driver Abdel Rahman Abbas died after gunmen opened fire on their car early on New Year's Day.

"We sentence the first four defendants to death by hanging," Reuters news agency quoted Judge Sayed Ahmed al-Badri as saying.

Earlier, the US embassy in Khartoum urged its citizens to keep a low profile if there was a guilty verdict.

A fifth man, who had provided the men with the weapon but did not participate in the murder, was sentenced to two years in prison at the court in the capital, Khartoum.

Mr Granville, 33, was an employee of the US Agency for International Development (USAID).

America's Federal Bureau of Investigation sent agents to help with the investigation into the killing and suspects were arrested the month after the fatal shooting.

Relations between Sudan and the United States have long been strained, most recently because of the conflict in Darfur.

Khartoum denies accusations that it mobilised Arab militias to take revenge on the local population six years ago, in what the US and others have called a genocide.