BERLIN -- Hundreds of German police used anti-terrorism laws Wednesday to raid the offices and apartments of globalization opponents they fear could disrupt next month's Group of Eight summit with firebombings and other attacks.
Security officials also announced tighter border controls ahead of the summit June 6 through 8 in the northern resort town of Heiligendamm.
Some 900 federal and local police officers in Berlin and other cities searched about 40 offices and apartments used by several left-wing activists and groups, they said.
Prosecutors said they were investigating more than 18 people suspected of organizing what they called a terrorist group that planned to carry out firebombings and other violence to hinder the summit of world leaders.
"The militant extreme left groups and their members are suspected of having founded a terrorist group, or of being members of such an organization, with the specific goal of staging fire bombings and other violent attacks in order to disrupt or prevent the upcoming G-8 summit in Heiligendamm," federal prosecutors said in a statement.
Germany's interior ministry announced it would tighten border controls to screen out violent protesters. People can usually travel freely within the European Union, but individual countries maintain the right to tighten checks for security purposes.
Violence has marred past summits, particularly in 2001 in Genoa, Italy, when police and protesters clashed in the streets for days.
Federal prosecutors said the raids focused on dismantling a computer server where they said many leftist groups maintained Web sites and mailing lists.
Activists, who will hold approved marches in nearby Rostock ahead of the summit, said the raids were aimed at silencing protests against the G-8, disrupting communication among anti-globalization groups and tracking down the names of individuals involved in them.
Some of groups that were targeted in the raid planned to block roads leading to Heiligendamm on June 6 to prevent politicians, journalists and service staff from reaching the summit, said one activist.
"The consequences of these searches for us is that it will bring the groups closer together and we will continue to mobilize for a massive blockade of the G-8 summit," said Tim Laumeyer, a member of the Anti-Fascist Leftists of Berlin.
Police took copies of the group's mailing lists and data on their computers. Investigators also searched private apartments, a photo archive, left-wing publishing houses and community centers.
"The goal of the raids was to collect information about potential disruptions during the G-8 and intimidate activists ahead of the summit," said Christoph Kliesing, a lawyer for the protesters.
A member of Gipfelsoli Infogruppe, a group that collects and spreads information about protests against the G-8, said that their Web page had been down all day.
"They cut the cable of the server," said Matthias Monroy of Gipfelsoli. "This is really awful for us -- all our information about the protests is not accessible anymore and we don't know if we will be able to retrieve all the material."
German security officials have built a $17-million fence around the northern seaside resort of Heiligendamm, hoping to keep protesters away. German Chancellor Angela Merkel is hosting the event, and the leaders of the United States, Russia, Britain, France, Italy, Canada, and Japan are to attend.
The protesters say they oppose the G-8 summit because the world's rich leaders ignore the suffering of people in developing countries while unrestrained globalization helps big business at the expense of the environment and workers.