Pakistani troops seized a camp used by the extremist group blamed in the Mumbai attacks and arrested more than 12 people, militants and a security official said Monday. The raid was the first known action by Islamabad in response to the attacks, which have sharply raised tensions between nuclear-armed rivals Pakistan and India and raised concerns in Washington over its campaign against al-Qaida in the region. India says the Mumbai siege was carried out and plotted by Pakistani militants belonging to the banned Laskhar-e-Taiba. It and the United States are demanding Pakistan crack down on the perpetrators. Troops briefly exchanged fire with people at the camp during Sunday's raid close to the town of Muzaffarabad in the Pakistani part of the disputed Kashmir region, the militants said.