Association of Southeast Asian Nations (ASEAN) foreign ministers "expressed serious concerns over the on-going developments" in the sea, which is subject to a web of bitter overlapping claims, on the eve of a leaders' summit in Naypyidaw.
Tensions in the South China Sea soared this week after Beijing moved a drilling rig into waters that are also claimed by Hanoi, sparking a stand-off in which Vietnam said its boats were attacked.
The incident drew a statement of concern from the United Nations.
The ASEAN ministers "urged all parties concerned... To exercise self-restraint and avoid actions which could undermine peace and stability in the area" in a statement issued today.
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The statement also called on claimants to "resolve disputes by peaceful means without resorting to threat or use of force".
Indonesian Foreign Minister Marty Natalegawa said the ministers' meeting was dominated by maritime rows.
China and Vietnam, which fought a brief border war in 1979, have been locked in a longstanding territorial dispute over their contested waters, and frequently trade diplomatic barbs over oil exploration, fishing rights and the Spratly and Paracel Islands.
The Philippines and Vietnam are the most vocal critics of China's claims among the 10-member bloc.
But the South China Sea is also claimed in part by ASEAN members Brunei, Malaysia and the Philippines as well as Taiwan.
Natalegawa said the ASEAN statement was aimed "to be in support of peace and peaceful settlement of disputes".
Singapore Foreign Minister K. Shanmugam said ASEAN did not want to take sides.