Four men working at a hospital construction site in northern Kenya near a refugee camp and the border with Somalia were shot dead by Islamic militants.

       A group of eight workers were resting on Friday when they were attacked, leaving four shot dead at close range.

       The other four workers escaped unharmed, a police source told the AP news agency.

       The hospital construction site is near Kenya’s largest refugee camp, Dadaab, and the border with Somalia where the al-Shabab militant group is based.

       Garissa County has in the past been attacked by al-Shabab militants who cross through the porous border.

       READ MORE ISIS horror as 'more than 60 Christians killed' including army officer

       Local police say the Friday attack may have been staged by an armed group that had warned the contractor to stay away from the area, which they consider their turf.

       Northern Kenya has in recent days seen violence that has left several people dead in different locations.

       On Wednesday, police at the Mandera border point recovered an improvised explosive device that was about to detonate.

       DON'T MISS: ISIS tells Americans they’ll 'drink their blood' in terrifying attack threat [EXCLUSIVE]

       Last week, two herders were killed at a watering point also in the Mandera area by gunmen.

       In April, five people were killed in a donkey cart explosion in Elwak town.

       The government says security operations in northern Kenya have been increased.

       The recent attacks have forced the government to suspend plans to reopen the 700-kilometre (434-mile) Kenya-Somalia border that was closed in 2011, though illegal crossings are still rampant.