Punjab state authorities cracked down on dissent Saturday, banning a convention called to forge a new unified political group and rounding up scores of politicians and human rights activists.

The authorities banned the convention, called by Sikh leader Simranjeet Singh Mann and planned for Sunday, saying it would become a forum for "seditious messages on behalf of the leaders of militant organizations."Punjab, a north Indian state with a powerful Sikh militant campaign for a separate homeland, has been administered under direct rule from New Delhi for the past three years.

"Under the cover of so-called unity, there is a sinister design to coerce right-minded persons into submission to the mandate of militants," an official spokesman said. "The government cannot be a silent spectator to anti-national activities."