Factbox: Major oil tanker spills since 1970

The Panama-registered tanker was sailing from Iran to South Korea, carrying 136,000 tonnes of condensate, an ultra light crude. That is equivalent to just under 1 million barrels.

The damage and volume of oil spilled are not yet known.

Tanker incidents causing large oil spills - greater than 700 tonnes - have steadily reduced from an average 24.5 a year in the 1970s to 1.7 on average per year since 2010, according to the International Tanker Owners Pollution Federation (ITOPF).

Below is a list of the major oil tanker spills since 1970 from ITOPF's database:

2007: Hebei Spirit off South Korea - 11,000 tonnes

2002: Prestige off Spain - 63,000 tonnes

1999: Erika off France - 20,000 tonnes

1996: Sea Empress off Wales, United Kingdom - 72,000 tonnes

1991: ABT Summer off Angola - 260,000 tonnes

1989: Khark 5 off Morocco - 70,000 tonnes

Exxon Valdez, Alaska - 37,000 tonnes

1983: Castillo de Bellver off South Africa - 252,000 tonnes

1979: Atlantic Empress in the Caribbean - 287,000 tonnes

The tonnages include all oil lost, including product which burnt or remained in a sunken vessel.

(Reporting by Josephine Mason; Editing by Susan Fenton)