Russian hostages released

Eight Russian workers kidnapped in a raid on their heavily-guarded home in Baghdad are reported to have been released today.

In an audacious assault, masked gunmen had killed two armed guards and then snatched the group of power workers as they relaxed in an inner courtyard.

The targeting of foreigners in their homes in the capital represents an escalation in the insurgents' tactics. Until now most abductions have been opportunist kidnappings on isolated highways near known troublespots.

Up to 40 foreigners are thought to be captive or missing in the wake of violence that has claimed the lives of at least 70 coalition troops and 600 Iraqis this month.

Seven Chinese hostages seized in Fallujah were released yesterday.

Meanwhile US forces are massing outside the holy cities of Najaf and Kerbala in preparation for a "final offensive" against the rebel Shia cleric Muqtada al-Sadr.

Local reports spoke of " dozens" of tanks and armoured vehicles on the outskirts of Najaf. Leaflets warning the residents of Kerbala not to fight back have been dropped by American aircraft over the city.

Lieutenant-General Richard Sanchez, commander of US ground forces in Iraq, said: "We have manoeuvred forces into the vicinity of Najaf to ensure we are prepared to conduct offensive operations to eliminate the final elements of Muqtada al-Sadr influence down there."

Early today, al-Sadr's Mahdi Army appeared to waver. Militiamen left many police stations in Najaf, though they still controlled others and continued to patrol the streets.

Al-Sadr himself is believed to be in Najaf or the nearby town of Kufa. General Sanchez said the "mission" of the US forces was to kill or capture him. Shia clerics, including the spiritual leader, Grand Ayatollah Ali Sistani, warned the Americans not to attempt such an operation.

With criticism of US " heavyhandedness" in the Sunni town of Fallujah, coalition strategists hope to intimidate al-Sadr's militiamen into leaving Najaf without a fight. Any full-scale offensive in the city, the holiest shrine in Sunni Islam, would be catastrophic for tense relations between Iraqis and the US occupation.

US commanders also said they were seeking "at least" two additional brigades - about 10,000 to 15,000 troops - after 10 days which have seen 73 Americans killed, the bloodiest period endured by coalition forces in Iraq.

Fallujah hospital director, Rafie al-Issawi, said about 600 Iraqis died in the city last week because of the American offensive. "Most are women, children or elderly, and not all the young men who died are insurgents," he said.

About 280 Iraqis have been killed by the Americans elsewhere in the country since 4 April, according to a tally of statements from Iraqi police, hospitals and the US military. US spokesman, Brigadier General Mark Kimmitt, denounced the figures as "propaganda," but admitted at least 700 "enemy" had been killed.

The US was yesterday struggling to maintain control over even the most important