Royal Dutch Shell plans to go ahead with drilling exploratory wells off Alaska and will use additional precautionary measures in light of the massive oil spill in the Gulf of Mexico.

In a letter to the US Minerals Management Service (MMS), Shell President Marvin Odum outlined nine additional measures that will help to handle any potential oil spill in the Chukchi and Beaufort Seas.

Shell said it will build a prefabricated coffer dam to halt a leak and increase the test frequency of a blowout preventer to every seven days from every 14 days.

Environmental groups in Alaska, however, have urged the US government to suspend Shell’s exploratory drilling with claims it will be difficult to prevent or respond to spills in hostile Arctic conditions.

Shell has paid $3.5bn for Chukchi and Beaufort oil leases, off northwest and northern Alaska. It plans to begin exploration work in July.

The MMS estimates that the area contains 15 billion barrels of recoverable oil and close to 81 billion gigajoules of natural gas.