BEIJING (REUTERS) - The South China Sea dispute is not a problem between China and the Association of Southeast Asian Nations (Asean) and China opposes certain member states trying to use it to sow discord, its foreign ministry said.

South-east Asian foreign ministers voiced "serious concerns"on Saturday over naval clashes between Vietnam and China as the regional group's top official urged Beijing to step up efforts to advance talks on maritime security.

Foreign ministers and heads of state of the 10-member Asean are facing a test of unity at their summit this weekend in Myanmar as some members express alarm over China's growing assertiveness in the disputed South China Sea and push for a strong joint statement.

China's foreign ministry, in a statement late on Saturday, said the issue was not "a problem between China and Asean".

"The Chinese side is always opposed to certain countries' attempts to use the South Sea issue to harm the overall friendship and cooperation between China and the Asean," the ministry said, in apparent reference to Vietnam and the Philippines, two of the most vocal countries on the dispute.

China was ready to work with Asean to continue implementing the Declaration on the Conduct of Parties in the South China Sea, which was agreed on in 2002 to try to manage tensions in the seas, the ministry added.

"China hopes that the relevant Asean (members) will sincerely respect and implement the declaration and make positive contributions to peace and stability as well as maritime security in the sea," the ministry said.

Tensions ratcheted up last week after China positioned a huge oil rig in an area also claimed by Vietnam, with each country accusing the other of ramming its ships in the region close to the disputed Paracel Islands.

China says territorial disputes should be discussed on a bilateral basis. It claims the entire South China Sea, putting it in conflict with Taiwan, Vietnam, the Philippines, Malaysia, and Brunei. The last four are Asean members.