Phnom Penh (AFP) – Cambodia accused Thailand on Monday of striking deep inside its territory, bombing the province that is home to the centuries-old Angkor temples -- the country's top tourist draw -- for the first time in a reignited border conflict.

Five days of fighting in July killed dozens of people before a truce was brokered and then broken within months, part of a long-standing conflict rooted in the colonial-era demarcation of the countries' 800-kilometre (500-mile) frontier.

Renewed fighting between the Southeast Asian neighbours this month has killed at least 31 people, including soldiers and civilians, and displaced around 800,000, officials said.

Each side has blamed the other for instigating the fighting, claiming self-defence and trading accusations of attacks on civilians.

Cambodia, which is outgunned and outspent by Bangkok's military, said Thai forces had expanded their attack "deep into" Cambodian territory on Monday.

Cambodia's defence ministry said in a statement that a Thai fighter jet had bombed "near a displaced civilians camp in the area of Srei Snam district, Siem Reap province".

The area is located less than a two-hour drive from the the Angkor temple complex and its top tourist attraction, the UNESCO heritage site Angkor Wat.

Cambodia's Information Minister Neth Pheaktra told AFP it was the "furthest that the Thai military has struck into Cambodian territory" during the renewed clashes -- more than 70 kilometres (43 miles) from the border and far from a disputed area.

The minister said it was also the first time Thailand's military had bombed areas of Siem Reap province.

The bombing forced hundreds of already displaced families to flee an evacuation site, he added.

Cambodia relies heavily on its tourism sector, which, as in many nations, is still recovering from the Covid-19 pandemic years.

Foreign tourist arrivals to Cambodia last year topped 6.7 million, the highest annual total on record, tourism ministry data showed.

But arrivals from July to September this year were down by about a third compared to 2019, the year before the pandemic.

Monthly ticket sales to the Angkor archaeological park were down at least 17 percent year-on-year from June to November, according to data from operator Angkor Enterprise.

Chhay Sivlin, president of the Cambodia Association of Travel Agents, told AFP that some tourists who planned to visit Cambodia via a Thai border crossing have cancelled plans or changed routes to go through neighbouring Vietnam or Laos.

She said the reports of bombing in Siem Reap province made "some tourists who have booked their trips already worry very much".

Some have cancelled travel plans while others have asked to delay their trip, she added.

US President Donald Trump, who intervened in the conflict earlier this year, said last week the two countries had agreed to a ceasefire beginning Saturday night.

But fighting raged over the weekend and into Monday, and Bangkok denied Trump's claim of a truce.

Thai Prime Minister Anutin Charnvirakul -- who dissolved parliament last week, paving the way for elections next year -- posted on Facebook on Sunday that his government would keep up the fight.

Military officials on both sides said clashes and strikes along the border were ongoing on Monday.