UTTARAKHAND DGP Abhinav Kumar on Friday said action under the stringent National Security Act will be taken against those who attacked police personnel and indulged in arson and vandalism in Haldwani. The DGP along with ADG (law and order) AP Anshuman visited the violence-hit town in Nainital district to assess the situation in consultation with senior officials. Six rioters were killed in the violence that broke out over the demolition of an illegally-built madrasa here, officials said on Friday. A curfew was imposed and shoot-at-sight orders were issued Thursday when violence erupted in a Haldwani locality. A high alert has been sounded across the State after the demolition of an illegally-built madarasa.