French security forces have launched a massive security operation in the run-up to the Group of Eight summit, which begins on Sunday.
German forces have been flown in to support their Swiss counterparts
Thousands of troops and police will outnumber the population of Evian - the spa town near the Swiss border that his hosting the meeting - by two to one.
Roads and railway lines are to be closed and demonstrations banned within 10 kilometres (6.2 miles) of the town.
The measures come in response to fears of violent demonstrations by anti-globalisation protesters and possible terrorist attacks.
The protesters are camping in an "intergalactic village" and anarchist settlement in the town of Annemasse, 40km west of Evian.
They opened an alternative summit on Thursday, and are planning a mass rally on the French-Swiss border on Sunday.
Organisers say they are expecting up to 100,000 people to take part.
The tight security has prompted some groups to plan unorthodox protests - one is planning to send rafts across Lake Geneva in an attempt to plant a pirate flag on top of the conference centre.
The leaders of the world's seven wealthiest countries plus Russia will be joined in Evian by the leaders of emerging nations such as China, Brazil, Nigeria and South Africa.
We haven't opened fire on a plane in France since World War II and I hope we won't have to do it
Air defence chief
Around 15,000 French troops and police will patrol the area, backed by several thousand Swiss and German security personnel.
Four security zones will be enforced in and around Evian from Thursday, of which the innermost will be restricted to world leaders and their entourages.
Combat aircraft and helicopter gunships will patrol the skies above the town, while anti-missile batteries will watch for signs of an attack.
The French part of Lake Geneva is closed to all but authorised traffic and police frogmen.
The French authorities are anxious to avoid a repeat of the Genoa summit in 2001, when police shot one man dead during running battles with protesters.
Tens of thousands are expected for Sunday's rally
There are fears that demonstrators could try to block the narrow road approaches to the town.
But there are also concerns about a possible terrorist attack, particularly between Evian and Geneva airport, where many dignitaries will be arriving.
"We've planned for this scenario, and we have measures in place to ensure that a plane hijacked in Geneva is not able to reach Evian," Patrick Thouverez, the French general in charge of air defences told AFP news agency.
"We haven't opened fire on a plane in France since World War II and I hope we won't have to do it," he added.