By Jonathan Saul and Catherine CartierLONDON, Aug 12 (Reuters) - A vast oil spill in the Gulf is quickly becoming one of the world’s worst in years after being allowed to spread almost unchecked for weeks, according to international agencies, satellite imagery and environmental groups.The slick off the coast of Oman from a grounded tanker carrying Russian crude had reportedly reached the mainland by Wednesday, the U.N.'s shipping agency told Reuters.

CAIRO, Aug 10 (Reuters) - Leaking crude oil from a tanker grounded off a nature reserve in Oman has created a slick covering almost 400 square kilometres, the country's government…

An oil spill from a damaged sanctioned vessel carrying Russian crude oil is continuing off the coast of Oman, with the slick now covering an area of approximately 390 square…