Thailand and Cambodia exchanged heavy artillery fire for a second day on Friday as border fighting intensified and spread, while Cambodia's leader said Thailand had agreed to a Malaysian ceasefire proposal but then backed down.

Cambodia has called for an "immediate" ceasefire with Thailand, after two days of cross-border fighting between the two South East Asian neighbours. Cambodia's ambassador to the UN, Chhea Keo, said his country asked for a truce "unconditionally", adding that Phnom Penh also wanted a "peaceful solution of the dispute".

Cambodia is seeking to "internationalise the issue to serve its own political objectives", Thailand’s ambassador to the United Nations Cherdchai Chaivaivid told a closed-door UN Security Council meeting.

Of course, trouble at the 508-mile (817 km) shared border is nothing new. For over a century, Thailand and Cambodia have contested sovereignty at various undemarcated points in the thick jungle punctuated with culturally-significant temples albeit with scant strategic or economic value.

Cambodia has accused Thai forces of breaching a previous agreement by crossing into Cambodian territory and carrying out what it describes as “unprovoked and deliberate attacks” near disputed temple areas.

But the fiery bout in Southeast Asia also marks a test for Washington's waning influence in a region viewed as a crucial theater in a geopolitical competition between the United States and China. "This crisis represents a critical test of American and Chinese influence in Southeast Asia,

Thailand favours bilateral negotiation rather than third-party mediation to resolve its military conflict with Cambodia, two Thai officials said on Friday, as fighting along their disputed border continued unabated.