We view the threats as totally serious, but hope that with joint efforts we can solve all the problems

Russian security chief Yevgeny Murov

As well as the threat of street unrest, Italian authorities have been warned that attempts may be made on the lives of some of the world leaders present.

One threat passed on to Italy by the German secret service is of an assassination plan by Saudi dissident Osama bin Laden, aimed at US President George W Bush. Militant supporters of Bin Laden are said to planning a possible bomb attack.

President Putin's personal security will also be stepped up because of a possible threat from Chechen rebels, say his bodyguards.

Italian senators made their objections clear as Mr Berlusconi spoke

Mr Putin's bodyguards have already visited Genoa and met the heads of special services from nearly all the countries being represented there, said Russian security chief Yevgeny Murov, head of the FSO.

"Each special service works out its own method of providing security these days. Russia's Foreign Intelligence Service renders enormous assistance to us, and we are in a permanent contact with them," he said in an interview with the Russian newspaper Komsomolskaya Pravda.

He said his agency was aware of the Bin Laden threat, and was making its Genoa preparations in the light of them.

"We view the threats as totally serious, but hope that with joint efforts we can solve all the problems," said Murov.

Leaders from Italy, France, Canada, the UK, Japan and Germany will also be at the two-day summit, which starts on 20 July.

Italian authorities are preparing a huge force of 20,000 police and soldiers, backed by the threat of tear gas, water cannon and a formidable array of military hardware.

Italian plans

20,000 officers (against 2,000 in Sweden) Practice 'war games' being held Tear gas and water cannon lined up 15 helicopters, four planes, seven naval boats Rooftop squads, hidden cameras, satellite surveillance Presidents Bush, Chirac based on aircraft carriers

A "ring of steel" will be imposed on the city. Railway stations and motorway junctions will be closed, and flights into Genoa diverted.

In the city itself, the streets around the summit venue have been declared as a "red zone", and will be blocked off by dozens of armoured vehicles. Outside the red zone, some areas will be set aside for protesters to make their views known.

Italian Prime Minister Silvio Berlusconi has said he wants dialogue with the protesters, and stresses the legimitate right of people to make their views known, but he has warned them that violent extremists will be "isolated and not be allowed to do harm".

Aircraft carriers

As the security operation continues to build up, some organisers are still reported to be keen to switch the summit venue to a cruise ship, which would be moored safely out at sea somewhere along the Italian Riviera.

At least two conference leaders - President Bush and French President Jacques Chirac - are already planning waterborne accommodation. Both will stay on aircraft carriers while attending the summt.

Concern about security has deepened since events in Gothenburg, when Swedish police appeared to be overwhelmed by the scale and depth of violence.

A lavish dinner had to be cancelled and some delegations had to switch hotels after police said they could no longer guarantee their safety.

Three protesters were shot and dozens of police officers were hurt.