Chinese state media are warning of potential long-term environmental damage from a Yellow Sea oil spill that went virtually unreported for two weeks.

A spokesman for China's largest offshore oil and gas producer is quoted Tuesday in the Communist Party-controlled Global Times denying any attempt to cover up the spill off northeastern Shandong province.

The spokesman for China National Offshore Oil Corporation insists the company notified relevant authorities immediately after the spills, and they are now largely under control.

However, news of the spills appeared only in blogs and Internet reports until Friday, when ConocoPhillips China confirmed the incidents in an e-mailed statement to the Beijing Times.

In a report on the incident Tuesday, the official China Daily says dead seaweed and rotting fish have been washing up on an island near the oil leak and that local fishermen are worried about the long-term effects.

The newspaper also quotes local officials on Nanhuangcheng Island saying the oil companies have not spoken to them about the spill.

China National Radio quoted an oil company official Sunday saying the oil spill at one point covered an area of just 200 square meters. But a local newspaper in Shandong said the oil slick was about 3 kilometers long and 30 meters wide.

The offshore oil field is jointly operated by CNOOC and ConocoPhillips, with the Chinese-based company having a 51-percent interest.