Thailand strongly rejected accusations it used chemical weapons against Cambodian troops in fighting that extended into a second day Saturday and has killed 10 soldiers and forced thousands of civilians from their homes.

Firing by both sides had ceased by noon, but Cambodia's defense ministry said at nightfall that the situation was "still tense."

A Cambodian defense ministry statement earlier charged that Thailand had fired 75 and 105 mm shells "loaded with poisonous gas" into Cambodian territory, but did not elaborate. A Cambodian field commander said separately that Thailand used both cluster shells _ anti-personnel weapons banned by many countries _ and artillery shells that gave off a debilitating gas.

The defense ministry accused Thailand of seeking to seize two ancient temples in disputed border territory and said Thai aircraft supported the attacks, including reconnaissance planes that "flew deep into Cambodia's airspace."

"I'd like to categorically deny that the Thai military has used any kind of aircraft," Thai Foreign Minister Kasit Piromya said at a news conference in Bangkok. "I'd like to reiterate that the accusations from Cambodia hold no truth at all. What they said about us using poisonous gas was not true either."

Col. Tawatchai Samutsakorn, commander of Thailand's 2nd Army Region, denied absolutely that cluster bombs or poison gas had been employed by his forces in the new fighting.

Col. Suos Sothea, deputy commander of Cambodia's artillery unit, had told The Associated Press by phone the six rounds of cluster shells had landed in villages about 20 kilometers (12 miles) inside Cambodia, but caused no casualties since people had already been evacuated. He also said Thai forces fired shell with "poison smoke" that caused several soldiers who inhaled it to lose strength in their arms and legs, but did not kill anyone.

Cluster munitions contain dozens or hundreds of small grenades or 'bomblets' that scatter over vast areas. Some can lie dormant for decades until disturbed, posing enormous danger to civilians.

Thailand acknowledged using cluster type munitions in border fighting in February, but argued that they were not of the type banned from use by 108 countries under an international treaty. Thailand has not signed the pact but has publicly pledged not to use such weapons.

Friday's fighting was the first reported border clash since February, when eight soldiers and civilians were killed near Cambodia's Preah Vihear temple. The new clashes took place about 100 miles (160 kilometers) west of there.

Saturday's fighting, mostly a long-distance artillery duel, began shortly after 6 a.m. and halted before noon, both countries said. Friday;s fighting also took place mostly in the morning.

Thailand's Tawatchai said one Thai soldier died Saturday, bringing the two-day casualty toll to four dead and 17 wounded. He said 15,000 civilians had been evacuated from the area of fighting.

Cambodia's Suos Sothea said three soldiers from his country had been killed Saturday, bringing Cambodia's two-day death toll to six. He said he could not give an accurate count of the wounded, though the Bayon TV station, closely linked to the government, reported five people hurt. Six Cambodian soldiers were reported wounded Friday. The TV station said 5,000 civilians had been evacuated from the danger zone.

The countries have competing claims over small swaths of land along the border, with nationalistic politics fueling tensions. Clashes have erupted several times since 2008, when the 11th-century Preah Vihear temple was given U.N. World Heritage status over Thai objections.

Indonesia, chair of the Association of Southeast Asian Nations, has called for an immediate cease-fire and further efforts to resolve the border dispute.

The flare-up comes as the Thai military raises its profile in domestic politics ahead of a general election expected to be held by early July. The army had previously effectively vetoed an agreed-on plan to station Indonesian observers to monitor the border situation.

Thai Foreign Minister Kasit said Saturday that he was ready to sign on a letter accepting Indonesia's offer of observers, and was waiting for agreement from Thailand's defense minister, expected this coming week.

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Associated Press writer Thanyarat Doksone in Bangkok contributed to this report.