Gunmen abducted around 100 Iraqi factory workers today as they were being ferried home from work in a fleet of buses just north of Baghdad.

The abduction, prompting fears of another horrific sectarian massacre, came on a brutal day in Iraq in which a senior member of Saddam Hussein's defence team was murdered after men in police uniforms grabbed him from his home.

Officials said that five busloads of employees from an industrial area at Taji, 20 miles north of Baghdad, were commandeered by dozens of gunmen in at least five minibuses. One source put the number abducted at over 100.

Large-scale abductions of Iraqi soldiers, police and civilians have been a feature of sectarian insurgent violence in the past couple of years. Several have resulted in massacres, where those abducted have later been gunned down by the road.

Taji, which is near to a major US air base, hosts two Saddam-era weapons factories and is in an area that has seen substantial activity by Sunni Arab militants.

Separately, an al-Qaeda-linked group announced that it would kill four Russian Embassy staff abducted 18 days ago in an attack in Baghdad in which a fifth Russian was killed. The group had demanded Moscow's withdrawal from Chechnya and the immediate release of all Muslim prisoners.

"After granting the Russian government 48 hours to meet our demands and their failure to do so ... the Islamic court of the Mujahideen Shura Council ruled to kill them," said the statement posted on a militant website. "And let them be an example for those who follow them and challenge the mujahideen and dare to step foot in the land of honour, Iraq."

Te Shura Council is a grouping of seven Iraqi insurgent groups, most prominent among them al-Qaeda in Iraq, that also claimed responsibility for the killing of two American soldiers abducted last Friday.

In Baghdad, a senior member of Saddam's defence team, Khamis al-Obeidi, became the third lawyer representing the former dictator and his seven co-accused to have been killed since the crimes against humanity trial began in October last year.

Police sources said that Mr al-Obeidi was abducted from his home at 7am by men dressed in police uniforms. He was shot dead and his body dumped on a street near the Shia slum of Sadr City.

His assassination came two days after the chief prosecutor demanded a death penalty for Saddam and three former aides for their roles in an alleged massacre on Shia villagers in 1982.

Khalil al-Dulaimi, who heads Saddam's defence team, blamed Shia death squads which Sunnis believe have infiltrated the Interior Ministry for the assassination.

"We strongly condemn this act and we condemn the killings done by the Interior Ministry forces against Iraqis," he said.

On the day after the trial started, Saadoun Janabi, defending the former head of Saddam’s Revolutionary Court, Awad Hamed al-Bander, was abducted from his office and killed.

Three weeks later Adil al-Zubeidi, representing Saddam’s half brother Barzan al-Tikriti and his former vice president Taha Yassin Ramadan, was ambushed and killed.

Most of the lawyers representing Saddam and his co-defendants now live outside Iraq, only entering Baghdad to attend the court. Mr al-Obedei chose to stay, stating simply: "Whatever will be, will be."

Mr al-Obedei's killing has dealt a further blow to the tempestuous trial, which has struggled along against a backdrop of killings, threats and the resignation of the previous chief judge. The defence team and human rights groups have long argued that a fair trial within Iraq is impossible.

The defence team has claimed that prosecution witnesses have been coerced into giving evidence of killings and torture. It has suggested that some of the 148 villagers alleged to have been rounded up and killed in response to a failed assassination attempt are still alive.

The defence team is due to begin closing arguments on July 10, bringing the trial to an end. The defendants face execution by hanging if convicted.

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