A Yemeni court on Saturday overruled earlier rulings and imposed harsher sentences, including a death sentence, on three militants convicted of attacking a French oil tanker and a helicopter carrying U.S. employees of an oil company.

Fawaz al-Rabeiee (search), a Yemeni, was originally sentenced to 10 years in prison but the appeals court issued the death penalty for his involvement in the October 2002 attack of the tanker Limburg (search) and planning to kill the American ambassador to Yemen and bomb five western embassies.

A group of 15 Yemeni men, including al-Rabeiee, were charged with plotting attacks in the country. All have been apprehended, with the exception of Yasser Ali Salem (search), who is believed to be a key plotter of the Limburg attack. He has been sentenced in absentia to 10 years in jail.

Two other convicted militants, Omar Said Jarrallah and Fawzi Halabi, had their sentences increased by five years to 15 years for working with al-Rabeiee on the same attacks and plots.

Besides imposing harsher penalties on the the three, the court upheld the death sentence against Hazam Majali, who was convicted of killing a Yemeni police officer at a checkpoint in 2002.

The 15 have one last chance to appeal to the supreme court to reverse their sentences.

The appeals court upheld sentences against 11 other defendants from the same group. Four had been sentenced to 10 years in prison and six defendants were sentenced to five years in jail. Another was sentenced to three years in prison for falsifying documents relating to the attacks.

Prosecutors in October demanded harsher penalties.

Al-Rabeiee was put on an FBI wanted list in February 2002 after his name was mentioned in interviews with detainees in Afghanistan and Cuba, where some Al Qaeda operatives are being held.

Two suicide bombers rammed an explosive-laden boat into the Limburg, killing a Bulgarian crew member and spilling 90,000 barrels of oil into the Gulf of Aden — an operation similar to the attack of the USS Cole, an America destroyer, off the coast of Yemen two years earlier.

The other attack targeted a helicopter carrying U.S. employees of the Texas-based Hunt Oil Co. (search).

The court hearing was held under strict security measures. Streets near the court building were blocked and several armored vehicles and military jeeps armed with machine guns surrounded the building.

Yemen, the ancestral home of Al Qaeda leader Usama bin Laden, is a tribal-dominated country at the southern tip of the Arabian Peninsula. It has long been a haven for Islamic extremists and the scene of numerous terrorist attacks, including the USS Cole bombing in 2000 that killed 17 American sailors.

Following the Sept. 11, 2001, attacks on the United States, Yemen's government joined the American-led war on terror and cracked down on militants operating within its borders.