Fifty-nine members of a hard-line Muslim group were taken in for questioning Wednesday following a bloody attack on an interfaith rally in the Indonesian capital, lawyers and police said.

More than 1,500 troops were deployed at the headquarters of the Islamic Defenders Front (FPI), which has a long record of torching buildings of rival groups, vandalizing nightspots and hurling stones at Western embassies.

Among those detained was FPI leader Rizieq Shihab, the alleged mastermind of Sunday's attack on hundreds of Christians, moderate Muslims and minority sect members, said national police spokesman Abubakar Nataprawira.

Most were being questioned, he said, but Shihab and 19 others have already been named suspects.

A dozen people were injured by gangs wielding bamboo sticks, triggering calls by lawmakers and activists for the hard-line group to be disbanded. They said the government, which relies on the support of Islamic parties in Parliament, has stood by silently long enough.

Indonesia is a secular nation with more than 220 million Muslims, more than any other country in the world. It has a long history of religious tolerance, but an extremist fringe has grown louder in recent years.

The FPI claims tens of thousands of followers. Fearing violence during or after Wednesday's arrests, security forces deployed in full force outside the front's main Jakarta headquarters.