Akal Takht jathedar Giani Harpreet Singh, who had convened a meeting of panthic organisations on Monday, issued a 24-hour ultimatum for the release of all supporters of Khalistan sympathiser Amritpal Singh, arrested by the Punjab police since the launch of its crackdown on March 18. The jathedar, on Saturday, had urged the fugitive chief of Waris Punjab De to surrender and face the legal process.