China Oilfield Services Limited (COSL) completed the first phase of oil drilling and exploration off Zhongjian Island of the country's Xisha Islands on Tuesday, the company said in a statement.

According to a plan made by its client, the exploration operation has moved to another site for its second phase work, the COSL said.

The company said it has acquired related geological data during the first phase of exploration.

The operation, carried out by the HYSY981 drilling platform managed by COSL, started on May 2 and is expected to be completed by mid-August.

The waters for the first phase were 17 nautical miles from Zhongjian Island, completely within China's territorial waters, while they are as far as 130-150 nautical miles (241-278 km) from Vietnam's coastline.

However, Vietnam had carried out intensive disruptions of Chinese company's normal oil drilling since May 2.

The company is a subsidiary of the China National Offshore Oil Corporation, the country's largest offshore oil and gas producer.