BEIJING (Reuters) - China has called for all sides in the South Sudan conflict to stop fighting, China's foreign ministry said, just as the U.N. Security Council approved plans to almost double the number of peacekeepers in the world's newest country.

The conflict in South Sudan has killed hundreds and some 45,000 civilians are seeking protection at U.N. bases. Violence erupted in the capital, Juba, on December 15 and quickly spread, dividing the land-locked country of 10.8 million people along ethnic lines.

The fighting has also affected oil production, which accounts for 98 percent of government revenue in South Sudan. It has forced Chinese state-owned China National Petroleum Company, a major oil investor in South Sudan, to evacuate some of its workers.

China's foreign ministry said in a statement late on Tuesday that deputy foreign minister Zhang Ming had said China is playing close attention to the conflict and the impact it was having on South Sudan's neighbors.

"As South Sudan's friend and partner, China calls on all sides of the conflict to ... immediately cease hostile actions, and open negotiations as soon as possible", the statement quoted Zhang as saying.

The remarks were made at a meeting with diplomats from member states of the East African Intergovernmental Authority on Development (IGAD), a seven-nation development organization that includes Sudan and Kenya, the statement said.

Zhang also said China supports the IGAD sending a mediation team to South Sudan.

Last week, Chinese state news agency Xinhua said an oilfield in the northern part of South Sudan, operated by a consortium of Indian, Malaysian and South Sudanese companies, was caught up in unrest that killed 14 South Sudanese oil workers.

Foreign Ministry spokeswoman Hua Chunying told a regular media conference on Tuesday that no Chinese nationals have been reported harmed in the conflict.

Later on Tuesday, the 15-member U.N. Security Council, which includes China, unanimously authorized a plan by U.N. Secretary-General Ban Ki-moon to boost the strength of the peacekeeping force in South Sudan to 12,500 troops and 1,323 police.

(This story was refiled to fix typographical error in headline)

(Reporting By Adam Rose; Editing by Paul Tait)