Nine civilians were killed in rocket strikes as fresh violence broke out this morning amid a bitter border dispute between Thailand and Cambodia.

Footage shows smoke billowing out of a gas station, which was reportedly hit by artillery, in Si Sa Ket province on July 24.

The Thai army said at least nine people, including two children Bandit Aunjit and Namkhong Boontang aged seven and eight, were killed in the crossfire while at least 14 were injured.

Thailand said it had scrambled F-16 fighter jets to the area as authorities condemned Cambodia as 'inhumane, brutal, and war-hungry'.

But Cambodia claims that the Thai military initiated the clashes over disputed land, which it has occupied since the International Court of Justice (ICJ) ruled in favor of Cambodia in the 1960s.

Locals in Kantharalak said they heard gunfire as the clash erupted at 9 am. The skirmish continued for more than two hours as officials evacuated more than 40,000 people from the area.

Both the Cambodian and Thai sides have accused each other of opening fire first.

The Royal Thai Army reported that Thai military officers at Prasat Ta Muen temple in Surin, heard the sound of an unmanned aerial vehicle at 7:35 am but could not pinpoint its location.

Six armed Cambodian soldiers, including one with an RPG, then approached the barbed wire area in front of the Thai base, prompting Thai soldiers to shout at them to stop.

At 8:20 am, the Cambodian side reportedly fired in the opposite direction of the base to the east of the castle before artillery fire was launched around 9 am.

Jirayu Huangsap, spokesman for the Prime Minister's Office, said the government received military information and 'clear evidence' that the Cambodian side initiated the attack.

However, Cambodian PM Hun Manet said Thailand initiated the attack this morning, forcing him to retaliate.

He wrote in a letter to the United Nations security council: 'Considering the recent extremely grave aggressions by Thailand, which have gravely threatened peace and stability in the region, I earnestly request you to convene an urgent meeting of the Security Council to stop Thailand's aggression.'

Cambodian troops reportedly fired continuous artillery rounds using 122mm rockets from BM-21 rocket launchers at residents in Surin, where one civilian was killed and a five-year-old child and his family were severely injured. Seven soldiers were also injured in the rocket strike.

The Thai army closed all border checkpoints at 8 am, while the Ministry of Foreign Affairs was instructed to compile evidence of the alleged provocations from the Cambodian side to lodge a formal complaint with international organisations.

The Royal Thai Embassy in Phnom Penh has advised Thai residents in Cambodia to leave as soon as possible. It also urged the public to avoid non-essential travel to Cambodia until the situation is resolved.

The Cambodian Ministry of National Defence condemned Thailand for alleged encroachment.

Prime Minister Hun Manet said Cambodia 'had no choice' but to respond with its armed forces against 'armed aggression'.

The clash flared several days after a border landmine exploded, injuring three Thai soldiers, including one who lost a leg.

Tensions between Thailand and Cambodia escalated after a clash between troops from both countries in a disputed area in Nam Yuen district, Ubon Ratchathani, on May 28, resulting in the death of a Cambodian sergeant.

Thailand expressed its intention to resolve the dispute through existing bilateral mechanisms. However, Cambodia vowed to take the case before the International Court of Justice in The Hague.

Thailand and Cambodia have a fractious history. The Khmer Empire, a precursor to modern-day Cambodia, once stretched across much of Southeast Asia before the ancient leaders moved their base south to Phnom Penh in the 16th century amid water shortages. The abandoned land was then taken over by the Siamese kingdom.

Thai leaders even supported Germany and Japan in WWII, before aiding the Americans in the bombing of Vietnam, Cambodia and Laos. They then helped the genocidal Khmer Rouge and provided sanctuary for their fugitive leaders.