Oil from a vast slick leaking from the ​grounded tanker Caroline Bezengi is reported ‌to be reaching Oman’s mainland, the UN’s shipping agency said on Wednesday.

“Oil is drifting offshore ​to the northeast of (Oman’s) Al-Qibliyyah Island, ​with some oil reported to be reaching ⁠the mainland. Oil spill contingency planning ​is in place,” a spokesperson at the ​International Maritime Organisation (IMO) said.

The slick off a nature reserve in Oman has created a slick covering ​almost 400 square kilometres, the country’s government ​said on Monday.

The tanker was carrying around 800,000 barrels ‌of oil from Russia bound for Asia, grounded off the coast of Oman on June 30, and is around 22 nautical ​miles off ​Oman’s fishing ⁠village of Sharbithat, the IMO spokesperson said.

“Oil has been leaking ​from the vessel for some time. ​The ⁠seasonal monsoon has limited access to the vessel and delayed salvage operations,” the ⁠IMO ​spokesperson said, adding that the ​agency was closely monitoring the leak.