Vietnam's prime minister raised the issue of South China Sea at an ASEAN summit Wednesday, calling on countries to refrain from complicating the situation.
"The East Sea situation remained complex so far, with large-scale reclamation being carried out on many rocks and submerged features, changing their original status," PM Nguyen Tan Dung said at the Association of Southeast Asian Nations (ASEAN) Summit in Naypyitaw, Myanmar's capital.
Vietnam have protested China's illegal land reclamation and construction of new facilities, including airstrips, on several reefs of the Spratly Islands, which is claimed by Vietnam.
Dung urged ASEAN nations to be more active and have more responsibilities in maintaining peace, security and stability in the region.
"ASEAN needs to continue requesting related parties to respect and fully abide by the DOC, especially Article 5, which stipulated that all parties must practice restraint and refrain from broadening or accelerating tensions and complicating the situation," he said.
China, Taiwan and four ASEAN nations have competing claims in the sea where concern is growing about an escalation in disputes even as the claimants work to establish a code of conduct to resolve them, Le Luong Minh, ASEAN secretary-general, told Reuters in Myanmar's capital.
"We are seeing a widening gap between the political commitments and the actual actions, the real situation at sea," he said.
In May, China sent an oil drilling rig and its armada to Vietnamese waters.
An ASEAN summit held in the same month issued a statement that expressed deep concerns about the tensions, which it said affected peace, stability, maritime security, safety and freedom.
United Nations Secretary-General Ban Ki-moon warned that competing territorial claims "could hold the region back," though he is encouraged by recent steps to enhance dialogue, which he hopes will prevent "any needless escalation."
"Leaders have a responsibility to resolve their disputes peacefully, through dialogue," Ban said at this week's ASEAN Summit.
"An Asia that can overcome legacy issues and look to a shared future will be even better placed to advance prosperity for all," he said.
Philippines President Benigno Aquino has said he would address what was a pressing security issue in Myanmar, but indicated some progress on Tuesday during a "meeting of minds" with Chinese counterpart Xi Jinping at an Asia-Pacific summit in Beijing.
China should focus on resolving disputes through international law and dialogue, US deputy national security advisor for strategic communications Ben Rhodes said on Tuesday.
"There cannot be a situation where a bigger nation is simply allowed to bully smaller nations," he told reporters in Beijing, where Obama attended the summit.
Singapore sees the maritime disputes as one of the region's biggest threats to security, Foreign Affairs Minister K Shanmugam told reporters.
Singapore will push for progress on a code of conduct that will reduce the potential for disruption to trade, he said.