Two oilfield platforms in China's Bohai Bay are estimated to have leaked 1,500 barrels of oil, or 240 cubic meters, following two oil spills last month, the operator ConocoPhillips said on Thursday.

The oil spill was discovered at the platform B and C at the Penglai 19-3 oilfield, which was ordered by the country's oceanic authorities to halt production on Wednesday.

ConocoPhillips said it would lose about 17,000 barrels of oil a day after the suspension.

The U.S. oil giant said it would not resume production until spill risks were eliminated. No oil slick has been found on the coast, and no casualties were reported.

ConocoPhillips China (COPC), a subsidiary of the U.S.-based energy giant ConocoPhillips, operates platforms in the Penglai 19-3 oilfield under an arrangement with the China National Offshore Oil Corporation (CNOOC), China's largest offshore oil producer.

ConocoPhillips said it used 3,000 meters of oil absorption columns and 33 vessels to fend off the spill.

The State Oceanic Administration (SOA) said the measures that COPC took to eliminate the risk of new spills had been inadequate.

An area of 3,400 square km in China's Bohai Bay has been affected by the spills, and 840 km of the bay was seriously polluted, which sent water quality ratings in the area to their lowest level, the administration said.