His personal files, containing the names and addresses of colleagues in both the party and the labour federation he led, were also stolen, his humble home ransacked.

The scene resembled the interrogation rooms of deposed president Saddam Hussein's security forces, whom officials suspect in the murder. Saleh may or may not have given them information; his files certainly did.

'The people who did this are very clearly members of the Ba'ath Party from the former regime,' said Mohammad Jassem al-Abad, a leader of the Communist Party, which is participating boisterously in the run-up to the imminent parliamentary elections that insurgents violently oppose.

'The way they killed him makes it very clear they're the ones who did this. It is their methods. His assassination wasn't random. It was perfectly chosen.'

Twenty months after the American invasion, the country's increasingly grotesque violence remains a shadowy phenomenon.

Many victims are Shi'ites and Kurds in the security forces or serving in official life, including the communists.

Hussein's old security officials appear to be settling scores against old enemies.

And they are destabilising the January 30 elections, which are certain to hand control to the Shi'ite majority and Kurds.

'These people have blood on their hands and are murderers,' said one high-level Justice Ministry official. 'They want everyone hiding behind walls, so they can control the streets.'

Most of Hussein's supporters came from Sunni Arabs in Tikrit, Mosul and Fallujah, the troubled areas where the US and the interim government face the most violent resistance.

A majority of the insurgents captured or killed, and up to 95 per cent of those detained, are Iraqi Sunnis.

But the insurgents are an ideologically mixed lot, experts say. They include Sunni Arab nationalists enraged by the US occupation. There are also foreign Islamic extremists - perhaps followers of Osama bin Laden or Jordanian terror leader Abu Musab al-Zarqawi. Criminals carrying out sabotage and murder for money are also involved.

The insurgents attack the security forces, officials and infrastructure, to sap the public's confidence in the government, according to a draft report on the insurgency written by military expert Anthony Cordesman.

They attack the United Nations, embassies and aid organisations, to drive the international community out of Iraq. They brutally kidnap and murder foreign nationals like Margaret Hassan, of Care International, to grab international media attention, spread horror and scare foreigners out of the country.

They hope their acts of savagery will provoke equally violent responses from the occupation forces and its allies in the interim government, which in turn will breed more insurgents and more anger towards the Americans.

'The more horrifying the attack, or incident, the better,' Mr Cordesman wrote.

The insurgents' fatal flaw may be their divergent ideas for the future of Iraq. All want the US out, but what comes afterwards is unclear.

Some wish to establish an Islamic utopia, and others want to reassert the supremacy of Iraq's Sunni Arab minority.

Others may simply want the anarchy to continue, to protect themselves from the wrath of those they tormented for decades.

If the insurgency has a brain, US and Iraqi officials say, it comes from well-trained intelligence operatives of the previous era, the ones who ambushed Saleh and tortured him before killing him, the ones who tied up 18 young men - some as young as 14 - and coldly executed them one by one.