Authorities raid a cultural centre in Hamburg as part of a major security operation in six northern states in Germany over concerns that left-wing radicals are planning to disrupt next month's G8 summit. German authorities on Wednesday (May 9) launched raids in six northern states and said they would impose new border controls over fears left-wing radicals were planning attacks to disrupt a June G8 summit on the Baltic coast. In Hamburg authorities raided the cultural centre "Rote Flora" and arrested several protesters. Some 900 security officials were searching 40 sites in Berlin, Brandenburg, Hamburg, Bremen, Schleswig-Holstein and Lower Saxony, the federal prosecutor's office said in a statement, adding it had opened two separate investigations. "They are being accused of putting together a terrorist group. In this context we raided 40 sites across the country today," Petra Kneuer, spokeswoman for the prosecurots said. German Chancellor Angela Merkel will host the leaders of Britain, Canada, France, Italy, Japan, Russia and the United States at the June 6-8 summit, which will focus on climate change, African poverty and economic cooperation. Germany has not experienced any major left-wing violence since the militant Red Army Faction (RAF), which waged a bloody two-decade long campaign of killings and kidnappings, announced in 1998 that it was disbanding. But authorities are taking aggressive pre-emptive measures to ensure the summit goes as smoothly as the World Cup did. A 2.5-metre high steel fence, topped with razor wire, has been placed in a 14-km ring around Heiligendamm and police will control access through airport-style X-ray machines. Around 40 km down the coast from the Kempinski Hotel where the leaders will meet, officials in the city of Rostock are expecting a demonstration of up to 100,000 people on the weekend before the event. Tim Laumeyer, the owner of a Berlin shop selling t-shirts and music whose store was raided on Wednesday (May 9) said the federal criminal police (BKA) were using the terrorist threat as an excuse to justify actions directed against the potential protesters at the G8 summit. "But the raids show that they want to criminalise G8 summit opponents. They want to differentiate between good and bad globalisation opponents," Laumeyer said. Hamburg, where a group of radical Arab students plotted the Sept. 11 attacks on the United States in 2001, is the nearest major German city to Heiligendamm.