China's top maritime official on Thursday urged U.S. oil giant ConocoPhillips to finish cleaning up oil spills in north China's Bohai Bay before the arrival of a deadline set by the government, stating that the company will face "enhanced supervision" if it does not do so.

Liu Cigui, head of the State Oceanic Administration (SOA), said his administration is collecting evidence and gauging the ecological impact of the spills in preparation for possible legal action against the company.

"Any company that damages China's oceanic environment must pay for their actions," Liu said during a teleconference concerning the handling of the incident, during which he referred to the spills as the "worst oceanic environmental accident" in Chinese history.

During a press conference held on Wednesday, Georg Storaker, president of ConocoPhillips China (COPC), said his company will be able to finish cleaning up the spills before the deadline arrives.

The SOA previously ordered COPC to "take all effective measures" to clean up the spills and eliminate any possible oil spill sources before Aug. 31. The SOA said on Wednesday that it will be ready to sue ConocoPhillips over the spills after it finishes assembling its legal team.

Storaker said his company has not yet received any demands for compensation but insisted that they will discuss the issue with Chinese authorities in the event of a lawsuit.

In a response to Storaker's remarks, Liu said China will demand compensation for the damage done to its environment in the wake of the spills and consider the "overlapping impact" caused by the spills.

"Regarding ConocoPhillips' performance in containing the oil spills, we will let facts and technicians speak," Liu said.

According to the SOA, 49 Chinese law firms have applied to provide legal assistance in the suit. The number of applicants will be whittled down to eight before the SOA assembles the final version of its legal team around the end of August.

ConocoPhillips China, a subsidiary of ConocoPhillips, first reported the oil spills in June. The spills have spread to beaches in Hebei and Liaoning provinces and been blamed for losses in local tourism and aquatic farming industries.

Although the company has worked to clean up the spills, pollutants have still been found in the bay, even after cleanup efforts were reported to be complete. ConocoPhillips China admitted that nine new oil spill sources have been found in the bay as of Aug. 20.

The SOA's North China Sea branch has conducted four major evaluations of the bay since the spills were reported.

Wang Fei, an SOA official, said on Thursday that a total of 5,500 square km of the bay's surface has been contaminated, with 870 square km seriously polluted, meaning that it is unfit for swimming and aquatic farming.