Southeast Asian leaders said China's island-building efforts in the South China Sea threaten to undermine the "peace, security and stability" of the region.
A statement issued at the end of the summit of the Association of Southeast Asian Nations, in Malaysia, noted "serious concerns" on Chinese land reclamation in the sea, calling for "self-restraint in the conduct of activities."
The ASEAN leaders’ concerns reflect growing tensions as China presses ahead with land reclamation projects in the disputed Spratly Islands.
A spokesman for China's Foreign Ministry, Hong Lei, defended the country's actions, saying its construction work was within its sovereign territory.
"The construction work by China on the islands and reefs in the South China Sea is totally within the sovereignty of China", he said. "It is fair, reasonable and legal, and it does not affect any other country."
Malaysian Prime Minister Najib Razak opened Monday's conference by urging the nine other ASEAN leaders to peacefully manage territorial disputes with China without increasing tensions in the region.
Najib urged the conclusion of talks that began in 2002 on a draft Code of Conduct governing how various nations should use the waters.
“We need to peacefully manage differences closer to home, including overlapping maritime claims, without increasing tensions," said Najib.
"Recent developments have raised concerns about the South China Sea — and given the importance of its sea lanes to international trade, it is natural that almost any occurrence there will attract global attention," he added. "ASEAN must address these developments in a proactive, but also in a positive and constructive way."
Tensions over the South China Sea’s waters have been intensifying after recently released satellite images showed significant construction underway by China in the disputed Spratly Islands, which are also claimed by the Philippines, Vietnam, Malaysia, Brunei and Taiwan.
The region around the islands is a potential source of energy resources, especially oil and gas. It is widely believed that Beijing is expanding the islands’ footprint to fortify them with military bases and airstrips.
The islands are more than 3,000 kilometers from China, but just over 860 kilometers from the Philippines and less than 800 kilometers from the cost of Vietnam.
The disputed waters of the South China Sea are widely seen as a potential flashpoint. In 2002, ASEAN and China signed a non-binding agreement to manage the disputes peacefully. And work on a legally binding Code of Conduct has been stretched out over the following years. The Philippines and Vietnam are leading the call for faster work on completing the Code, which is backed by the United States and other countries.
In 2012, China and ASEAN did make headway in talks on a drafting a Code of Conduct to ensure the regions states’ political, economic and territorial interests in the South China Sea are safeguarded.
Najib said he would be pressing for further gains in talks this week.
“As Chairman, Malaysia hopes that we will achieve progress in our efforts towards an early conclusion of a Code of Conduct,” he said.
Sunday, Philippines Foreign Affairs Secretary Albert Del Rosario called on ASEAN nations to adopt a tougher stance towards China and press for the “massive reclamations” to be “immediately stopped.”
Del Rosario charged that China was “poised to consolidate de facto control of the South China Sea” with wide ranging implications that he said would impact beyond the region.
Vietnam has also opposed Chinese claims in the South China Sea. And last year a Chinese oil rig that drilled in waters claimed by Vietnam set off violent anti-China protests. But analysts points to deep divisions within ASEAN — a region heavily dependent on China’s economy to drive growth — over a unified effort to counter China on the issue.
Beijing is a major investor and trading partner in Laos, Cambodia and Myanmar - countries which have no claims in the disputed Sea.
Nearby Thailand has shored up military ties with China, especially since the Thai military’s takeover in May last year, amid widespread criticism from the West, especially the United States.
In 2012, the deep divisions within ASEAN over China’s role in the disputed South China Sea, triggered tense debate at an ASEAN foreign ministers’ meeting, leading to an “unprecedented” failure to issue a final communiqué - the first such occasion in more than four decades.
ASEAN consists of Indonesia, Brunei, Vietnam, Cambodia, Laos, Malaysia, Myanmar, the Philippines, Singapore and Thailand.
