The United Naga Council UNC, an appex body of the various Naga tribes in Manipur, has imposed a 20-day economic blockade on the two National Highways of Manipur from Wednesday morning. The UNC is demanding among other things, dissolution of the newly elected Autonomous Hill District Councils, lifting of all prohibitory orders from the Naga inhabited areas and a judicial enquiry into the May 6 incident at Mao Gate in Senapati district. No commercial vehicles are plying on the Imphal Dimapur National Highway since Wednesday morning.