Police said Dar was abducted on Thursday evening by four militants who came in a car and seized him from Vehil village in Shopian district.
His bullet-riddled body was found on Friday morning in the adjacent Kulgam district.
Dar is the second security personnel abducted and murdered by the militants in south Kashmir in recent days.
He was earlier posted as the personal security guard of the Superintendent of Police of Shopian district.
Police said the constable had been part of many anti-militancy operations in south Kashmir in the past but was these days posted in Srinagar district.
On June 14 this year, militants abducted and murdered rifleman Aurangzeb Khan of Rashtriya Rifles when he was going to join his family in Mendhar area of Poonch district to celebrate Eid festival.
Aurangzeb too had taken part in many anti-militancy operations including the one in which a top militant commander, Sameer Tiger, was killed.
Militants also shot and critically injured an Imam, Muhammad Ashraf Thokar, in Parigam village of Pulwama district on Friday.
He was shifted to hospital in a critical condition. The Imam belonged to Bijbehara town of Anantnag district.
No militant group has so far owned the attack on the Imam.