KARACHI, Pakistan, April 15 (Reuters) — Tens of thousands of people rallied Sunday in Pakistan’s biggest city, Karachi, in opposition to a radical religious school that has begun a Taliban-style anti-vice campaign in the capital, Islamabad.

“The people of Islamabad are insecure and under threat due to the activities of these religious terrorists,” said Altaf Hussain, a Pakistani party leader who addressed the rally by telephone from London.

Mr. Hussain, who lives in self-imposed exile in Britain though his party, the Muttahida Qaumi Movement, is in the governing coalition, said the religious extremists in the Lal Masjid, or Red Mosque, in Islamabad and the adjoining madrasa, Jamia Hafsa, had hurt Islam’s image.

“Islam is a religion of peace and it does not need Kalashnikovs and sticks,” he said at the rally, while a helicopter whirled overhead and hundreds of police officers stood by.