Police said 105 people were still in custody on Friday morning after the clashes the previous day, which saw riot police fire tear gas to stop as many as 2,000 demonstrators marching on the heart of the summit city.
Masked protestors clad in black used wooden stakes to smash around a dozen bus shelters and set fire to rubbish bins, setting up a barricade before police disbanded the marchers and pushed them back towards their camp.
Around 25,000 police were on standby in the eastern French city to contain further protests during Friday and Saturday, which are expected to draw tens of thousands of people opposed to NATO's military operations. French authorities fear trouble from a hard core of some 2,000 protestors they consider violent and dangerous, and are alert to the threat of a terror attack from foreign extremists.
A German photographer working for the DPP news agency was injured in Thursday's clashes, his employer told AFP. A police spokesman said calm had been restored in the early evening.
Police said that there were between 500 and 600 protestors on Thursday. Organisers said there were 2,000.
The summit is being held in Strasbourg and in the German towns of Kehl and Baden-Baden.