More tankers came under attack in Gulf waters on Thursday as the US–Iran war escalated, and Iranian drones entered Azerbaijan, threatening to spread the crisis to more oil producers in the region.A Bahamas-flagged crude oil tanker was targeted by an Iranian remote-controlled boat laden with explosives while anchored near Iraq’s Khor al Zubair port, according to initial assessments. A second tanker at anchor off Kuwait was taking on water and spilling oil after a large explosion on its port side.Nine vessels have come under attack since the conflict broke out between the US, Israel and Iran on Saturday. Iran launched a wave of missiles at Israel early on Thursday and also sent drones into Azerbaijan, injuring four people.Meanwhile, Bahrain says an Iranian missile hit a state-run oil refinery. It said the fire on Thursday night was extinguished and the refinery was still working.