Terrorists had attacked a GREF camp around 2 a.m. in Battal area in Akhnoor sector of the IB, a police officer said.
“Three labourers working for GREF were killed in the terror attack,” he added.
Reports from the area said the terrorists, whose exact number was not known, managed to escape after the attack.
Police have started searching inside and around the camp, he added.
However, the attackers were yet to be traced, he said.
High alert was sounded in Jammu district in general and in Khour tehsil in particular.
The GREF is the parent cadre force of the Border Roads Organisation (BRO) that builds and maintains border roads in the country.
This was the first terror attack in Jammu in 2017.
The last terror attack took place on November 29, 2016 when terrorists wearing police uniforms attacked an army camp in Nagrota area of Jammu.
Seven soldiers, including two officers, were killed in Nagrota terror attack.
Terrorists had also attacked a Border Security Force camp in Samba district the same day.