Royal Dutch Shell and Statoil have been granted permission to conduct seismic surveys in the oil-rich Chukchi Sea off north-west Alaska.

The National Marine Fisheries Service issued permits allowing the companies to operate among protected marine mammals.

US District Court judge Ralph Beistline issued an amended order allowing Shell to conduct shallow-hazard surveys and scientific research in the Chukchi Sea even though broader oil exploration is suspended in the area.

Shell is to proceed with its shallow-hazard surveys, biological studies and ice-scouring studies in Chukchi, reports Reuters.

Meanwhile, Statoil said the company is proceeding with its $40m, two-month seismic programme in the Chukchi Sea where Statoil holds 16 leases.