IMPHAL, August 4: An Assam Rifles jawan was killed and a captain injured when armed activists launched an attack on the 8th Assam Rifles post at Toupokpi in Manipur's Bishenpur district on Tuesday night, official sources said on Wednesday. They said the attack took place around 1930 hours. The security personnel also fire back during the encounter which lasted for about 15 minutes. A jawan was killed on the spot and a Captain was seriously injured, they said. The militants escaped under the cover of darkness. Security forces have cordoned off nearby areas and launched a manhunt.