Protestors have launched a two-way assault on the Group of Eight summit as Greenpeace boats intruded into a maritime exclusion zone and protestors tried to block roads.
As leaders of the world's wealthiest nations began talks on limiting climate change, two Greenpeace boats raced across the Baltic Sea pursued by police vessels.
On land, police made about 100 arrests as demonstrators tried to get to a barbed wire security barrier around the summit venue.
During a ten-minute chase, one Greenpeace boat collided with a police speedboat as it tried to outmanoeuvre its chasers, throwing its four occupants into the water, close to the shore.
Greenpeace spokesperson Jo Kuper said the demonstrators were trying to reach the beach to hand over a petition to the G8 leaders. She added that three activists had been injured.
Activists in one of the boats were carrying a placard bearing the words 'G8 Act Now'.
Greenpeace said it had informed the police as soon as the boats penetrated the exclusion zone. 'There will be arrests, but we don't know how many,' Ms Kuper said.
Greenpeace said that protestors had used 11 inflatable dinghies in all, but most of them were intercepted by police and driven away from the exclusion zone.
The dramatic boat chase came after police denied a report in this morning's Bild newspaper that two large holes had been made in the underwater barrier off the coast of the hotel where the leaders were holding talks.
'There is no security breach, there is no hole or any sort of damage to the net,' a police spokesman said.
Protestors block road to summit
The three-day summit was hit on its first day by anti-globalisation protests which blocked roads to the Baltic resort of Heiligendamm where the G8 leaders are meeting.
Today, hundreds of demonstrators gathered for a second day around the 12km security fence surrounding the summit by the leaders of Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.
About 1,000 people also congregated near two key road access points which they had blocked on Wednesday when police used water cannon to force the activists off the road.
At the new road blockades, police said they had made around 100 arrests. Further blockades were expected later, a police spokesman said.
He added that a small group of violent demonstrators were trying to arm themselves with potatoes spiked with nails.
A spokesman for the G8 Block protest group, Christoph Kleine, described the road blockades as a success. 'We can't top that. Nobody can take away from us our success yesterday,' she said.
The anti-globalisation movement Attac said it would continue blocking roads until the end of the summit on Friday, but insisted its protest was peaceful.
About 16,000 police, many from anti-riot units, are on duty for the summit and a spokesman said reinforcements were being drafted in.
Axel Falkenberg, a spokesman for the special police unit set up for the meeting, said he hoped the demonstrations would subside.
