Oil prices rose $1 on Thursday after drones struck Iraqi Kurdistan oil fields for a fourth day, pointing to continued risk in the volatile region.

BAGHDAD (AP) — Drones targeted oil fields in Iraq’s semi-autonomous northern Kurdish region Wednesday, the latest in a series of attacks in recent days that have put several oil facilities out of commission.

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