Cambodia has accused Thailand of intensifying its bombardment of disputed border areas, even as officials from the two countries attend a multi-day meeting aimed at negotiating an end to deadly clashes.

The neighbours’ longstanding border conflict reignited this month, shattering an earlier truce and killing more than 40 people, according to official counts. About a million people have also been displaced.

Cambodian and Thai officials were in their third day of talks at a border checkpoint on Friday, with defence ministers from both countries scheduled to meet on Saturday.

However, Cambodia’s defence ministry said Thailand’s military carried out a heavy bombardment of disputed border areas in Banteay Meanchey province on Friday morning.

“From 6.08am to 7.15am, the Thai military deployed F-16 fighter jets to drop as many as 40 bombs, to intensify its bombardment in the area of Chok Chey village,” it said in a statement.

Thai media said on Friday that Cambodian forces had launched heavy attacks overnight along the border in Sa Kaeo province, where several homes were damaged by shelling.

The two countries blame each other for instigating the fresh fighting, which has spread to nearly every province along their border.

Both countries also claim to have acted in self-defence and accuse the other of attacking civilians.

The US, China and Malaysia brokered a truce to end five days of deadly clashes in July but the ceasefire was short-lived.

Earlier on Friday, the Cambodian prime minister, Hun Manet, said on Facebook that he had spoken by phone with the US secretary of state, Marco Rubio, and the two discussed “ways to secure a ceasefire along the Cambodia-Thailand border”.

The conflict stems from a territorial dispute over the colonial-era demarcation of their 800km frontier and a collection of temple ruins situated there.