SAN'A, Yemen -- A Yemen court sentenced a Muslim extremist to death Sunday for assassinating a key politician and planning attacks against three American missionaries, who were slain last year.

The sentencing immediately followed Ali al-Jarallah's conviction in the Dec. 28, 2002, death of Yemeni Socialist Party deputy secretary-general Jarallah Omar during an Islamic political conference.

Al-Jarallah was also convicted of coordinating the murders, two days later, of the three Americans at a Southern Baptist missionary hospital in Jibla, southern Yemen, and of forming a terror cell to kill local officials and foreigners.

The court also sentenced six convicted accomplices of al-Jarallah in the Omar murder to three to 10 years in prison.

Al-Jarallah, dressed in a blue prison uniform and sitting handcuffed behind bars, appeared composed upon hearing the verdict. He and the six others sentenced to prison terms said they would appeal.

Despite the decision for capital punishment, Omar's colleagues and his lawyer criticized the case's resolution, claiming judicial authorities failed to punish other Yemenis believed to have supported al-Jarallah.

"There are others involved who were not included in this verdict, such as the entities that financed him," lawyer Mohammed al-Mekhlafy said.

"Al-Jarallah was not working on his own. He is part of a financed organization ... and this verdict does not suffice in combatting terrorism in Yemen."

Omar's Socialist Party and other opposition parties had called for further investigations to reveal what they said were influential Yemenis financing al-Jarallah's cell.

The slain politician's family claimed the investigation was botched and that they were barred from reviewing the case file.

"It is not in anyone's interest that (the case) is closed within such a confined framework," said Mohammed al-Robaie, the head of a committee of Yemeni opposition political parties that followed Omar's case.

Abed Abdul Razak Kamel, who was sentenced to death in May for killing the American missionaries, told the court he had coordinated his attack with al-Jarallah.

On Dec. 30, 2002, Kamel walked through a hospital security checkpoint, concealing his weapon under loose-fitting clothes, and opened fire at a staff meeting.

He killed hospital director William E. Koehn, 60, of Kansas; purchasing agent Kathleen A. Gariety, 53, of Wauwatosa, Wis.; and Dr. Martha C. Myers, 57, of Montgomery, Ala.

Yemeni security officials have said Kamel and al-Jarallah may be linked to the al-Qaida terror network headed by Osama bin Laden, who has Yemeni ancestral roots. Police found bin Laden audiotapes at Kamel's house.

In its Sunday verdict, the court said al-Jarallah worked as a preacher in a San'a mosque where he incited youth against the government.

The court said al-Jarallah attempted to form a terrorist group, finance it and provide weapons and audiotapes propagating extremist ideas.