Southeast Asian and Australian leaders on Wednesday warned against actions that "endanger peace" in the South China Sea, following fresh confrontations between Beijing and the Philippines in contested waters.

Simmering tensions in the trade corridor threatened to boil over this week, when Chinese boats in the Spratly Islands were accused of hounding Philippines vessels.

Beijing on Wednesday accused the United States of using the Philippines as a "pawn to stir up trouble in the South China Sea" as hostilities between the Asian nations escalate over their territorial dispute.

China claims almost the entirety of the South China Sea as its own, ignoring legal precedents and competing claims from a host of Southeast Asian nations.

The festering dispute poses one of the region's most vexing security challenges, looming large during a three-day summit between Australia and the 10-nation ASEAN bloc.

"We encourage all countries to avoid any unilateral actions that endanger peace, security and stability in the region," read a joint declaration hammered out between ASEAN members and Australia.

"We recognise the benefits of having the South China Sea as a sea of peace, stability and prosperity," the statement added.

As the summit kicked off on Monday morning, Philippine foreign minister Enrique Manalo delivered a simple request to Beijing: "Stop harassing us".

The following day, Chinese coast guard boats were accused of harassing a flotilla of Philippine ships sailing a resupply mission.

The Chinese vessels were involved in two separate collisions, the Philippines coast guard said, and blasted one of the resupply boats with a water cannon.

Images taken in the aftermath showed the water cannon had shattered windows on the control bridge of one of the Philippine vessels.

Bound to act by consensus, the ASEAN forum has long struggled to make inroads on the overlapping claims staked throughout the South China Sea.

But the fraught atmosphere hanging over the region has some nations now pushing for the bloc to take a firmer stance.

Close United States ally Australia has proven increasingly willing to speak out against China.

"I am very concerned and Australia is concerned about any unsafe and destabilising behaviour in the South China Sea," Australian Prime Minister Anthony Albanese said on the summit's sidelines.

"We need to make sure that activity in the South China Sea alleviates any tensions and doesn't add to it," he added.

- Myanmar crisis -

The surging conflict in junta-ruled Myanmar also continued to frustrate ASEAN leaders, whose efforts to resolve the crisis remain largely fruitless.

Junta leaders have essentially ignored the bloc's five-point peace plan, painstakingly pulled together in 2021.

"We strongly condemn the continued acts of violence and call for immediate cessation," the joint declaration read, referencing what it termed Myanmar's ongoing "political crisis".

"We call for effective humanitarian assistance, and inclusive national dialogue."

Laos, a communist state with ties to crucial Myanmar ally China, is chairing ASEAN for the first time since 2016.

ASEAN's 10 member states are Brunei, Cambodia, Indonesia, Laos, Malaysia, the Philippines, Singapore, Thailand, Vietnam and Myanmar.

Although Myanmar remains a member, political representatives and military leaders from its ruling junta have been banned from high-level meetings.