Italian authorities had prepared a massive security force

Many protesters said they were beaten, strip-searched and denied access to lawyers.

In one incident police raided a school which was being used as a base by protesters.

Briton Mark Covell has threatened to sue the police after he was allegedly beaten unconscious in the raid.

He was arrested but eventually released without charge.

Mr De Gennaro said in his evidence to the commission that summit unrest had been started by "violent criminals".

But it had led "in some cases to an excess in the use of force from certain units," he said.

Berlusconi: Wants UN summit moved abroad

Around 2,500 anarchists were present in Genoa, he estimated, from countries including the UK, Germany, Greece, Spain and the US. Others protesters also joined the violence, he said.

Three senior officials, including Mr De Gennaro's deputy, were moved to new duties by the government last week.

The violence has left many Italian politicians reluctant to host further international meetings.

On Tuesday, the mayor of Naples, Rosa Russo Jervelino, called for next month's planned meeting of Nato defence ministers in the city to be postponed.

Senior politicians, backed by Silvio Berlusconi, have also called for a UN World Food Summit, due to be held in Rome in November, to be moved abroad.