An oil spill from the tanker Caroline Bezengi off Oman has expanded into one of the biggest spills in years, with satellite analysis reviewed by Reuters putting the slick at more than 2,000 square kilometers and the U.N.'s shipping agency saying some oil has reportedly reached the mainland. That is far larger than Oman's estimate of nearly 400 square kilometers and Greenpeace's earlier estimate of about 600 square kilometers. The 25-year-old tanker, carrying an estimated 800,000 barrels of Russian crude and operating under international sanctions, ran aground on June 30 at Al-Qibliyyah Island in the Hallaniyat marine reserve after first reporting difficulties off Yemen on June 8. Maritime sources said a blast appeared to have occurred aboard, though no party has claimed an attack. The vessel is part of the so-called shadow fleet moving Russian oil and had sailed from Novorossiysk in April before passing through the Suez Canal at the end of May on its way toward India. The spill threatens endangered turtles, humpback whales and coral reefs, while seasonal monsoon conditions, the lack of recognized Western insurance and the treatment of the case as an "act of war" are complicating response and compensation efforts. The IOPC Funds said it would not be involved in clean-up costs, and specialists say stabilizing the tanker and transferring remaining crude are becoming more urgent as the hull deteriorates.