Pakistan's anti-graft watchdog arrested former Prime Minister Imran Khan at Islamabad high court on Tuesday, in a dramatic move that threatens fresh turmoil in the nuclear-armed country. Footage of the arrest showed scores of security personnel in riot-control gear whisking Khan away in a van as Khan's party called for protests across the country. "Pakistan people, this is the time to save your country. You won't get any other opportunity," the Pakistan Tehreek-e-Insaf (PTI) party wrote on Twitter.