WASHINGTON - US Secretary of State Hillary Clinton on Wednesday welcomed the death sentences handed down against four Islamists in Sudan who killed a US aid worker and his driver.

"I believe the guilty verdicts handed down today are an important step in bringing justice for John Granville and Abdelrahman Abbas Rahama, US Agency for International Development (USAID) workers murdered in Sudan in 2008," Clinton said in a statement.

"They were dedicated to bringing peace and stability to Sudan and we honor their memory," the top US diplomat added.

Granville, 33, and Abbas, 40, were fatally shot in their car on January 1, 2008 while returning from a New Year's Eve celebration.

Authorities charged five young men with the double murder.

Judge Ahmed al-Badri handed down the much-anticipated sentence in a North Khartoum courtroom, where he sentenced four of the five to death.

Mohamed Mukawi, Abdelbasit Hajj al-Hassan, Mohammed Osman Yousef and Abdelraouf Abu Zeid Mohamed Hamza all received the death penalty for their roles in the killings.

The fifth defendant, Mourad Abdel Rahman Abdallah, received a two year prison sentence because his role was limited to supplying the weapon for the attack, the judge said.

Abdullah has been in jail since January 2008, making him eligible for release in January 2010.

Hamza, one of the four defendants sentenced to death, is the son of the head of a Sudanese Muslim group that is considered peacful and does not have a political affiliation.

The group, Ansar al-Sunna, is linked to Wahhabism, the conservative form of Islam dominant in Saudi Arabia.

Washington has had tense relations with Khartoum since the beginning of the 90s.

Sudan is on the US list of countries that harbor terrorists and became the target of US economic sanctions in 1997.

However, despite these differences, FBI agents cooperated with the Sudanese authorities to investigate the two murders.