If there has been recent instability, the report may explain why the US and Britain believed last month's air campaign had a chance of toppling Saddam Hussein's regime. On the other hand, it could equally be propaganda aimed at destabilising the country.
The killings and arrests came in the South of the country, the US State Department said, quoting Iraqi opposition forces. The South, home to Iraq's Shia muslim minority, was the scene of an uprising shortly after the 1991 Gulf War, which was viciously repressed by the Iraqi security forces
America has said that it would support any regime which overthrew President Saddam, and the Iraqi opposition has suggested establishing a "free zone" in the South.
"Over the past six weeks we have seen reports of mass arrests throughout the southern no-fly zone and in the Shia suburbs of Baghdad and hundreds of summary executions of dissidents at Amara and Radwania prison," said James Rubin, the State Department spokesman.
President Saddam's family, which directs key parts of the security apparatus, ran the crackdown, the US alleged. "The repression reportedly reached a peak in November, with hundreds killed in actions directed personally by Qusay Hussein," said Mr Rubin.
Qusay, Saddam's second son, runs the Special Security Organisation, a target of the air raids last month. The US had originally planned air attacks on Iraq in November, but these were halted at the last moment.
It now seems possible that the US timed its attacks to support a possible uprising in southern Iraq, since many of the targets were communications and military sites in the region.
The State Department said that more than 2,000 civilians from the southern marshes had been taken hostage, including women and children, against further outbreaks of violence by the Shia community.
t Iraq yesterday asked the United Nations to remove British and American staff from humanitarian teams working in the country. It said it could not guarantee their safety after the allied air raids last month. The demand covered 14 staff members - one American and 13 Britons. UN officials said the matter was still being negotiated.Reuse content