BAGHDAD (Reuters) - Gunmen shot dead a leading Iraqi judge in an ambush as he drove home in Baghdad, police and a judicial official said on Friday.

Kamel al-Shewaili, head of one of the capital's two appeals courts, was killed while driving along a road in eastern Baghdad on Thursday afternoon, said Abdul Satar al-Birqadr, a spokesman for the Iraqi Supreme Judicial Council.

Assailants using two vehicles blocked the judge's way, a police source said. They shot the judge, who was alone in his vehicle, before driving away, he said.

Usually, top Iraqi judges have bodyguards in their cars or in accompanying vehicles. Neither the police source nor Birqadr knew whether Shewaili had bodyguards with him.

"He was one of the best judges in Iraq. He worked in this field for more than 20 years. It is very difficult to replace him," Birqadr said, adding that the shooting was one of a series of killings of Iraqi professionals.

In January, gunmen killed appeals court judge Amir Jawdat al-Naeib, also a member of the Supreme Judicial Council, as he drove to work through western Baghdad.

Iraq's Supreme Judicial Council is a supervisory body which also nominates the chief justice and other senior posts.

Militants have frequently targeted judges, academics, other professionals and their families in bitter sectarian fighting between Shi'ites and Sunni Arabs.

The violence, in which tens of thousands of Iraqis have died, flared after the bombing of a Shi'ite shrine in Samarra in February 2006 and threatened to tip Iraq into all-out civil war.

Attacks against prominent individuals have become less frequent as violence has fallen in recent months during a security crackdown by U.S. and Iraqi forces.

(Reporting by Waleed Ibrahim; Writing by Adrian Croft; Editing by Ibon Villelabeitia)