Drones struck oilfields in Iraqi Kurdistan on Thursday, with officials pointing to Iran-backed militias as the likely source of attacks this week that have slashed the region's oil output by more than half.

No group has claimed responsibility, but the attacks have heightened tensions between Baghdad and Kurdish authorities, raising concerns about the region’s energy security.

A drone attack targeted an oilfield in Iraqi Kurdistan this Thursday, in what represents a big hit that lowers oil output between 140,000 and 150,000 barrels per day.