23 April 2011 Last updated at 08:35 GMT
Thousands of villagers have been evacuated from the area around the latest fightingAt least one soldier has been killed in fighting along the border between Thailand and Cambodia, raising the death toll to seven in two days.
Troops exchanged artillery and gunfire in jungle around Ta Krabey temple, which both sides claim.
The area is about 200km (125 miles) west of the disputed 900-year-old Preah Vihear temple, the scene of deadly clashes in February.
Thousands of civilians have been evacuated from the area.
The BBC's Rachel Harvey in Bangkok says it is not immediately clear what sparked the most recent violence.
"Fresh fighting started at around 0600 (2300 GMT Friday) with rifles and mortar shelling," said Thai army spokesman Col Prawit Hookaew.
"We are negotiating to stop the fighting," he added.
Thai officials said one Thai soldier had been killed and more than four injured. There were also unconfirmed reports that a Cambodian soldier had died.
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Rachel HarveyBBC News, Bangkok
Villagers had been evacuated February - some had moved back, some were still in evacuation centres and temporary accommodation.
But now we're hearing that between 7,000 and 10,000 villagers on the Thai side alone have been moved away from their homes, packing up their stuff as quickly as they can into the back of vehicles, with no knowledge of course of when it's going to be safe to go back again.
With munitions flying across the border in this jungle area it is a worry even if these villagers do then go back because there could then be unexploded ordinance in that area. So there's a short-term problem for villagers and a potential long-term threat as well.
Cambodia said artillery shelling had also taken place.
A Cambodian defence ministry spokesman described the fighting as more intense than that on Friday.
Until Friday, an informal truce had appeared to be holding.
Cambodia said three of its soldiers were killed on Friday and six wounded while a Thai spokesman told the BBC that three of its soldiers had been killed and 11 injured.
Both sides blamed each other for the fighting.
Indonesia, which has been negotiating peace talks between the two neighbours on behalf of the regional group Asean, has called for an immediate ceasefire.
Demarcation issueCambodia has made clear it wants international mediation, but Thailand insists the dispute can be resolved through existing bilateral channels.
However, events on the ground appear to be moving faster than the diplomatic process, our correspondent says.
Preah Vihear temple was awarded to Cambodia in 1962 by an international court.
But both sides claim ownership of the surrounding area, and there have been several skirmishes there in recent years.
Other parts of the Thai-Cambodian border have not yet been formally demarcated, causing continuing tensions between the two countries.
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