A huge security operation has been launched in the Czech capital, Prague, as 40 heads of state descend for a landmark summit of the Nato alliance this week.

Are we preparing for war?

Czech President Vaclav Havel

The summit will agree on the admission of up to seven new members, including the three Baltic states, and the creation of a new rapid reaction strike force.

Nearly 15,000 police, soldiers and special forces are on the alert for threats ranging from terrorist attacks to anarchist demonstrations, and US fighters are providing security in the air.

US President George W Bush arrived in the city on Tuesday, ahead of the summit on Thursday and Friday, after which he will fly immediately to Saint Petersburg for a meeting with Russian President Vladimir Putin.

Military doctrine

There's all kinds of ways for that coalition [against Iraq] to be formed - it could be formed with Nato if they chose

US President George W Bush

"I want Russia and President Vladimir Putin to understand there is no reason to fear Nato expansion," Mr Bush said in comments to Eastern European journalists published on Tuesday.

He added that Russia was no longer a threat to the West, and said that Nato's military strategies needed to be changed accordingly.

Before boarding a flight for Prague, he added that Nato could help form a coalition against Iraq.

Czech anarchists have already begun protesting

A new military doctrine to be adopted at the summit will place greater emphasis on the threat posed by international terrorism and arms of mass destruction.

To protect delegates at the summit - Nato's first behind the former Iron Curtain - a no-go area for ordinary people will be set up around the summit venue, and streets will be sealed off for official convoys.

The Czech army is supplying armoured cars, helicopters and anti-chemical weapons teams.

Its bomb disposal experts were called on to defuse a bomb found on a railway track in a Prague suburb on Tuesday.

The city's residents have been encouraged to take a long weekend, to get them out of the way.

Planes grounded

A helicopter lands to pick up Mr Bush in Washington

Because the Czech air force is unable to completely protect its airspace, US F-15 and F-16 jets will be patrolling the air, accompanied by two in-flight refuelling aircraft and an AWACS early-warning surveillance plane.

Private planes will be grounded for the duration of the summit, and armed guards will sit on board commercial flights.

Taken aback by the security measures, Czech President Vaclav Havel, has asked: "Are we preparing for war?"

He hopes the summit will be the crowning moment of his term as president, before he steps down in January.

Power cut threat

Thousands of militant protesters have vowed to converge on the city for the summit, including a group known as the Black Bloc, blamed for instigating much of the violence at the G8's Genoa summit in July 2001.

Last week police arrested several people they alleged were plotting cut power lines supplying the summit venue and the Prague underground railway.

Border guards have already turned away a number of known hard-line protesters on Interpol blacklists.