The ambitious targets, first reported by Reuters on Thursday, will likely cost the oil and ship industry billions of dollars to implement.

They are also set to raise the price of some fuels as the industry switches to cleaner-burning distillates, industry experts say. A key part of the legislation, approved by the IMO, relates to the tightening of harmful sulphur dioxide emissions. The regulations will be formally adopted in the autumn.

The industry source said the UN agency had agreed to impose sulphur limits in special Sulphur Emission Control Areas (SECA) of 0.1 percent by 2015 from the current 1.5 percen.

The tightening is needed to slash sulphur emissions in coastal areas, which SECA aim to protect, where they have proven to be a major health hazard in heavily populated areas.

"The 0.1 figure for the SECA is very significant because we are fairly sure the number and range of SECA will be quite extensive in the future," said Simon Bennett, secretary at the International Chamber of Shipping.

Some two-thirds of the 50,000-strong world fleet's movements, that carry 90 percent of the world's traded goods, are in coastal areas.

There are currently only two SECA -- in the Baltic and North Sea. Experts say that will likely expand significantly to include coastlines in the European Union and North America, among others.

"The all important million-dollar question is how many SECAS will there actually will be?" Bennett said.

Experts say the regulations, a revision of existing marine pollution laws, broadly fall into two phases.

The first will see cleaner burning distillate fuels substituted for sulphur-high fuel oils in SECA by 2015, followed by a gradual lowering of all sulphur content in fuels by 2020-2025.

That means ships in the middle of the ocean will be able to burn fuels higher in sulphur content until 2020, when sulphur limits also fall heavily to 0.5 percent.