The UN has called for a peaceful solution to the latest flare-up in the long-running border conflict between the two nations.

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.

Thailand and Cambodia exchanged heavy artillery fire for a second day on Friday as their worst fighting in over a decade intensified and spread to new areas.

Tensions have bubbled between the two neighbors for months, flaring on Thursday as Cambodia and Thailand exchanged fire.

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