Germany has stepped up security in recent days, officials said Friday, amid intelligence reports indicating a heightened threat of attacks against German troops in Afghanistan and suicide bombings in Germany itself. It follows the arrest in Pakistan of three suspected Islamic radicals, believed to be part of a group of 10 people trained to carry out suicide bombings, a top law enforcement official said. Joerg Ziercke, head of the Federal Crime Office, Germany's equivalent to the FBI, gave few details of the arrests. The suspects were young Germans who had converted to Islam and been radicalized, he said. However, a Pakistani official said one was Kazakh.