Mumbai: A US federal appeals court has ordered Royal Dutch Shell Plc to suspend oil exploration in the Beaufort Sea off the north coast of Alaska after environmental activists and Alaska Native groups filed a case against the company.

Shell has invested over $44 million for drilling up to four exploration wells during the brief Arctic summer. Shell''s drilling permit runs through October and the company has time till August to obtain a favourable ruling.

Hearings in the case are set for August 14 in San Francisco.

Shell''s detractors in the Beaufort Sea say that environmental impact studies carried out by Shell and approved by the US department of the interior failed to take seriously the threat posed to bowhead whales and other wildlife.

The interior department''s minerals management service approved Shell''s drilling plans in February.

Native whalers say they are concerned that hunting the whales, which they are permitted by the International Whaling Commission, could become more difficult and dangerous.

Shell had planned to drill four wells on the Sivulliq prospect this summer. Oil had been discovered at Sivulliq in the 1980s but the field was abandoned at the time due to the high cost of developing oil fields in the Beaufort Sea.

Shell''s exploration programme is considered to be the biggest ever to hit this offshore area.