NAYPYIDAW, Myanmar - Southeast Asian leaders have expressed "serious concern" over territorial disputes in the South China Sea, according to a statement released Monday, amid a growing row between Vietnam and Beijing over contested waters.
The communique from the 10-member Association of Southeast Asian Nations (ASEAN) follows a summit on Sunday that was dominated by escalating maritime tensions.
"We expressed serious concerns over the ongoing developments in the South China Sea," the statement said.
ASEAN called on all parties involved to "exercise self-restraint, not to resort to threat(s) or use of force, and to resolve disputes by peaceful means in accordance with the universally recognized principles of international law".
The ASEAN meeting came just days after both Vietnam and the Philippines squared off against China in different areas of the disputed sea, which is home to key shipping lanes and thought to contain huge energy reserves.
Observers say the statement marks a change of tone by the regional bloc, many of whose members have close economic and political ties with China.
The statement "represents a slight tightening of ASEAN's position," said Vietnam expert Carl Thayer, adding it suggests a rare level of "consensus" on the vexed sea rights issue.
But "the fact that no party was mentioned - conspicuously China - is standard ASEAN fare," he added.
Vietnam lobbied energetically at the meeting for a strong statement on the maritime issue from its regional neighbours.
In remarks to the summit, Vietnam's Prime Minister Nguyen Tan Dung urged his ASEAN counterparts to protest at China's controversial decision to move an oil drilling rig early this month into waters also claimed by Hanoi.
Reiterating accusations that Chinese vessels had then attacked Vietnamese ships in the disputed waters, he slammed Beijing's move as "extremely dangerous".
Dung also told the summit that Hanoi views the incident as a violation of international laws.
The spat between Beijing and Hanoi, which drew a statement of concern from the UN, has stoked large anti-China protests in Vietnam.
China and Vietnam fought a brief border war in 1979 and the pair frequently trade diplomatic barbs over oil exploration, fishing rights and the contested Spratly and Paracel Islands.
Disputes with China present a delicate challenge to the ASEAN bloc, some of whose members are closely reliant politically and economically on Beijing.
In 2012 China's ally Cambodia caused consternation when it was ASEAN head by refusing to take Beijing to task over its assertive maritime stance.
Beijing asserts ownership over almost all of the South China Sea, which is also claimed in part by ASEAN members Vietnam, the Philippines, Brunei and Malaysia as well as Taiwan.
Manila, which has asked a UN tribunal to rule on China's claims over most of the sea, also said last Wednesday it had detained a Chinese fishing boat in disputed territory.
The other ASEAN members are Cambodia, Indonesia, Laos, Myanmar, Singapore and Thailand.