The scene on the German side of the Rhine River was calm compared to Strasbourg, where French police detained at least 300 people last night and forced demonstrators back into a tent camp on the edge of the city. Demonstrators destroyed telephone booths and attempted to build barricades before they were stopped, said a police spokesman.
A total of 107 were still being held. Suspects can be held up to 48 hours before being formally charged.
In Kehl, traffic continued to move across the Europe Bridge that links France to Germany ahead of its closing and scores of police patrolled the area where a protest had been scheduled to begin at noon local time. France has temporarily reinstated border controls with its immediate neighbours for the meeting.
A group of 10 people unfurled a banner calling for "Peace" as police looked on. Near the bridge, one protester was surrounded by seven police who were searching his bag.
Police in patrol boats zipped up and down the Rhine while helicopters hovered overhead. Many police vans and units from across Germany were also on the scene. Elsewhere, police were playing cards and sitting in their police vans reading newspapers.
Strasbourg's streets were virtually deserted as unauthorised traffic was forbidden in many parts of the city. Schools and the university were closed. Most businesses and restaurants have shut down for the duration of the summit.
Christoph Kleine, a spokesman for the protest network Block Nato, told The Associated Press that some 3,000 protesters were encamped in Neuhof just south of Strasbourg and they planned to stage a demonstration on Saturday in the city centre.
"We do not want any clashes with police ... We will go around them, we will go through them," he said. "We will not attack them. But we will make our way."
German authorities estimate that up to 25,000 protesters will take part in several demonstrations in Baden-Baden and Kehl, while France's interior minister has suggested 30,000 to 40,000 ultimately could show up in Strasbourg, where a camp has been set up to house demonstrators.
German and French police have said 2,000 to 3,000 members of the violence-prone "black bloc" — so-called for the black clothes and hoods they wear — are expected.
Some 15,000 German police — including 31 riot squads — and 9,000 French police are on call for the summit.
Protest organisers have called for peaceful demonstrations to highlight their complaints, including anti-war, anti-globalisation, anti-capitalist and disarmament platforms.
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