An estimated 6,000 anti-globalisation protesters evaded police roadblocks on Wednesday and approached the fence around the G8 summit in Heiligendamm in defiance of a police ban.
Police used tear-gas and water-jets from special anti-riot trucks in a bid to drive part of the crowd back from the welded-mesh, steel fence erected at a radius of two km from the summit hotel.
The demonstrators had swarmed through woods and fields from their tent villages near Heiligendamm, an exclusive Baltic beach resort, just hours before the summit was to formally begin.
One of the protest columns, coming from the east, was pushed back as they approached the principal access road. Another group, from the west, came close to the fence and ran onto a second access road.
The protesters, hailing from several European nations, were mainly in their 20s, many wearing colourful casual dress or humorous costumes, but a few wearing the hoods and the black clothes that mark out militants.
A rail line used by a veteran steam train was also blocked. The line, used exclusively by tourists, joins Kuehlungsborn, where the summit press centre is located, with the beach resort.
A police spokesman said the special summit police force, which had met frequently beforehand with protest organizers, had not been surprised by the invasion. An adequate number of officers were at the scene to protect the fence from being breached.
The summit police force, drawn from several states, numbers 16,000.