Over 40 demonstrators were arrested across the country, although protests in most cities, including Berlin, Cologne, Hannover and Göttingen, remained largely peaceful.

The one exception was the northern city of Hamburg, where police resorted to water canons and truncheons in clashes with some 2,000 activists demonstrating in the district of St. Pauli.

The police were retaliating against demonstrators outside a local culture center who were throwing bottles and stones. The trouble had died down by midnight, with Hamburg police reporting that a total of 26 protestors had been arrested, and four people injured.

"Three police officers and one passerby were hurt," said a police spokesperson early on Thursday morning.

Complaints from the left

The raids also triggered outrage among politicians, with one complaint coming from Claudia Roth, co-head of the opposition Green party.

"(These raids) are inappropriate, arbitrary and undifferentiated," she said in Berlin Wednesday. She also described the swoop as a blatant attempt to intimidate and criminalize opponents of the summit.

The Social Democrats' youth wing, Jusos, was similarly adamant that the raids were an overreaction, while the Left party accused the government of encouraging "a climate of escalation."

Anti-G8 group "Gipfelsoli," meanwhile, referred to a "wave of repression" designed to undermine the movement's communication structures.

Agreement came from Christoph Kliesing, a lawyer who represents left-wing groups. "In my opinion the goal of the searches is to gain information about potential G8 summit actions and perhaps to scare those people who want to take part in the protests," he told a news conference in Berlin Wednesday.

Stepping up security

One month before the summit takes place in Heiligendamm, some 900 security officials searched 40 sites in Berlin, Brandenburg, Hamburg, Bremen, Schleswig-Holstein and Lower Saxony as part of two separate investigations into anti-globalization militants, the federal prosecutor's office said in a statement.

"We suspect those targeted, who belong to the militant extreme-left scene, of founding a terrorist organization or being members of such an organization, that is planning arson attacks and other actions to severely disrupt or prevent the early summer G8 summit in Heiligendamm from taking place," the prosecutor's office said.

The same day, Interior Minister Wolfgang Schäuble said he would be tightening border controls in measures similar to those taken during last summer's World Cup tournament to prevent an influx of soccer hooligans.

"We are particularly focused on dangers arising from violent globalization opponents," the ministry stressed.