Cambodian officials say their troops have clashed with Thai soldiers for a second day along a disputed border area.
Thai officials said at least one of their soldiers was dead.
The latest fighting began at dawn on Saturday and broke a truce agreed after a clash on Friday killed at least four Thai paramilitary troops and three Cambodian soldiers.
Each side blames the other for firing first in the disputed border area in the northeastern Thai province of Surin, Reuters reports.
Thousands of villagers on both sides of the border have been evacuated.
Thailand and Cambodia have been locked in a stand-off over the border since July 2008, when a temple in the area, Preah Vihear, was granted UNESCO World Heritage status.
Thailand opposed this on the grounds that the land around the temple had never been demarcated.
The last time fighting erupted, in early February 2011, ASEAN foreign ministers brokered a ceasefire deal under which both countries would allow unarmed military observers from Indonesia to be posted along their border.
That agreement has still be put into place.
