China's top offshore oil producer, CNOOC Ltd has restarted production of its southern Bohai Bay oilfields after a malfunction in April halted operations, the accident tainted firm said on Monday.

CNOOC's statement, sent to Reuters via email, comes after the firm halted production at two offshore oilfield platforms in the northern Bohai Bay earlier in July, due to slow progress in cleaning up oil leaks.

The oil major said the operation in its BoZhong 28-2 South oilfields were running smoothly and production capacity had recovered to the level before the incident, reaching approximately 39,000 barrels of oil per day.

In June, the company reported that leaks on the platforms B and C of the Penglai 19-3 oilfield in the northern Bohai Bay, were the fault of the field's US operator, Conoco Phillips, China's State Oceanic Administration.