The body of a defense attorney for one of Saddam Hussein's fellow accused, two bullet holes in the head, was found Friday dumped outside a mosque, two days after the man appeared at the opening of the former Iraqi leader's trial, Iraqi authorities said.

The New York-based watchdog group Human Rights Watch warned that the killing of the lawyer, Saadoun Janabi, would have a chilling effect on all sides in the trial and urged U.S. forces to provide security for anyone in the trial who asks for it.

"It highlights real concerns that we've had for quite some time about conducting the proceedings here in Iraq, considering the insurgency and the security challenges," said Richard Dicker, international justice director for the rights organization.

Dicker said there were indications some defense attorneys had turned down protection from Iraq's Interior Ministry, whose police forces many Iraqis believe are under the political control of the Shiite majority. "There can't be a fair trial if defense attorneys are not willing to vigorously defend their clients," Dicker said.

Lt. Col. Steven Boylan, a spokesman for U.S. forces, said he knew of no request to date by trial participants for protection by American troops. He said that in any case it was unclear whether they would have jurisdiction.

The identities of all but one of the judges and most other court officials were concealed by tight camera shots on the opening day of the trial on Wednesday. Witnesses in the trial will have the option of appearing with their faces screened, officials have said. But Janabi and the 12 other defense attorneys appeared on camera, sitting to the side of the eight defendants.

Janabi was representing Awad Haman Bander, the former head of Hussein's Revolutionary Court. Hussein, Bander and six others from the Sunni-dominated former government face death by hanging if convicted on charges of murder and torture in the 1982 executions of 143 Shiite men and boys from the town of Dujail after Hussein's motorcade was ambushed there in a failed assassination attempt.

The Associated Press reported that 10 masked men abducted Janabi from his Baghdad office Thursday. His body was found several hours later, said Col. Haitham Mohammed Ali, a spokesman for Iraq's Interior Ministry.

Hussein's chief attorney, Khalil Dulaimi, told the AP that defense lawyers had received threats recently by e-mail, cell phone text message and telephone. He did not specify if the threats came from Hussein opponents angry that the lawyers were defending members of his government, from Hussein supporters who felt that the lawyers should not cooperate with the current government by taking part in the trial, or from people with other motives.

The U.S. military on Friday reported that four service members were killed in western Iraq. A roadside bomb killed three Marines, and a separate attack by what the military called "indirect fire" -- a term that usually means mortar rounds or rockets -- killed a soldier attached to a Marine unit.

In other violence Friday, drive-by shootings in Baghdad killed four police commandos, an army captain and a mosque preacher, wire services said.

The bodies of another three policemen who had been blindfolded and shot in the head by insurgents near the Jordanian border were brought to Baghdad, police said. Another body, of a civilian, was found in central Baghdad, police told news agencies.

Correspondent Jonathan Finer contributed to this report.

Iraqis transport the coffin of Saadoun Janabi, the defense attorney for a co-defendant in Saddam Hussein's mass murder trial. Janabi was abducted Thursday.Saadoun Janabi appears in court at its opening session, a day before he was kidnapped and then shot.