Deadly clashes have escalated along the disputed Thai Cambodia border, as both sides blamed each other for the fighting and vowed to defend their territory.

Seven civilians in Cambodia have been killed, and 20 wounded, while three Thai soldiers have been killed in the fiercest fighting since a five-day conflict that erupted in July.

Both sides accused each other for violating a US-backed ceasefire deal signed in the presence of Donald Trump six weeks ago.

On Tuesday morning, Cambodia’s senate president, Hun Sen, said that “after being patient for more than 24 hours” to respect the ceasefire deal and evacuate civilians, Cambodia had retaliated.

“Cambodia needs peace, but Cambodia is compelled to counterattack to defend our territory,” he said in a Facebook post, saying his country had strong bunkers and weapons that would give it an advantage.

Hun Sen, who was prime minister for almost four decades, remains extremely powerful in Cambodia despite handing power to his son Hun Manet in 2023.

Thailand’s defence ministry spokesperson, Rear Admiral Surasant Kongsiri, told the media that Thailand was “determined to defend its sovereignty and territorial integrity and therefore military measures must be taken as necessary”.

The Thai prime minister, Anutin Charnvirakul, has previously vowed his government would do whatever necessary to protect its territory. “There will be no talks. If the fighting is to end, (Cambodia) must do what Thailand has set,” he said.

On Tuesday, the conflict spread further, with Royal Thai Navy announcing it was taking action “to expel” Cambodian forces that it said were encroaching on Thai territory in Trat province.

Thai military said Cambodia was using rocket launchers, bomb-dropping drones and artillery on Thai positions, and that artillery shells had fallen on two civilian homes in Sa Kaeo province. No casualties were reported.

Cambodia accused Thailand of firing into civilian areas, and said “renewed aggression” by Thailand had “destroyed infrastructure, damaged temples, cultural property, human heritage and disrupted essential public services”.

More than 125,000 people in Thailand are staying in temporary evacuation shelters across Ubon Ratchathani, Sisaket, Surin and Buri Ram provinces, according to the Thai military’s 2nd Army Area Operations Center. In Cambodia, more than 21,000 people have been evacuated across Preah Vihear, Oddar Meanchey, Banteay Meanchey provinces.

The dispute between Thailand and Cambodia dates back more than a century, to when France, which occupied Cambodia until 1953, first mapped the land border. Conflict over the border, which stretches across more than 508 miles (817km), has erupted repeatedly over the years.

Tensions rose in May, and escalated into a five-day conflict in July, when at least 48 people were killed and 300,000 displaced, before Trump brokered a ceasefire.

The ceasefire deal has appeared precarious, with both sides repeatedly accusing each other of violations. Last month, Thailand said it was suspending the ceasefire deal, accusing Cambodia of laying fresh landmines along the border, including one mine it said had wounded a Thai soldier.

A Cambodian civilian was later killed, and three wounded, according to the Cambodian prime minister, after both sides accused the other of opening fire.