NAYPYIDAW: Recent incidents in the South China Sea are a wake up call that a code of conduct is urgently needed to guide claimants' actions in the disputed resource-rich waters, said Prime Minister Lee Hsien Loong on Sunday.

He also called on Asean leaders to provide strong political support for the challenging process of negotiating such a code.

"We must now make urgent progress on the code of conduct to prevent future mishaps," he said.

With tensions rising in the disputed waters following a collision of vessels between China and Vietnam last week, days before the Asean summit here, Mr Lee said "such incidents could easily spiral out of control, trigger unintended consequences and undermine confidence in our region".

He therefore commended the Asean foreign ministers for issuing a stand alone statement on Saturday that underscored the importance of self restraint and peaceful resolution of disputes in the South China Sea, and called for the quick conclusion of a code of conduct.

Speaking at a retreat for Asean leaders, Mr Lee underlined the need for Asean to stay united in an uncertain global environment. He said that despite different strategic perspectives, the Asean 10 share fundamental interests as set out in the 1967 Bangkok Declaration, the association's founding document.

A united Asean is critical for member states to manage regional uncertainties that could overwhelm them individually, moderate the frictions in relations between major powers, and promote an open, inclusive and transparent regional architecture, he said.

"Conversely, a divided Asean undermines our credibility, and relevance to the world," he added.

Turning to the haze pollution that has hit the region in recent years, Mr Lee encouraged Asean members to adopt the Haze Monitoring System quickly.

He also said he looked forward to Indonesia's ratification of the Asean agreement on Trans-boundary Haze Pollution, thanking Indonesia President Susilo Bambang Yudhoyono for his leadership on it.