German police have arrested two men of Middle Eastern origin, suspected of buying chemicals for a bomb attack.
Officers searched an Islamic cultural centre and two addresses in Berlin after an investigation lasting several months.
The centre itself is not under suspicion but the pair are thought to have spent time there. They have been identified as a 24-year-old German-Lebanese man and a 28-year-old from the Palestinian Gaza Strip.
Germany has been spared a major terrorist incident but security was stepped up last November after intelligence reports of a heightened threat. The latest arrests come ahead of a visit by the Pope and the 10th anniversary of the September 11 attacks.