SURIN, Thailand -- Three Thai civilians were killed as heavy combat continued along the country's border with Cambodia, the Thai military said Thursday, marking the country's first civilian fatalities since the fighting resumed.

Trump announced the agreement to restart the ceasefire in a social media posting following calls with Thai Prime Minister Anutin Charnvirakul and Cambodian Prime Minister Hun Manet.

Armed clashes between Thailand and Cambodia entered a second day on Tuesday, both sides said, in defiance of calls from the United States to stop fighting and adhere to a months-old Trump-brokered peace deal that now looks on the brink of complete collapse.

President Trump helped end a simmering conflict between Cambodia and Thailand in the summer, but the ceasefire didn't last long.

Fighting has flared up several times this year since a Cambodian soldier was killed in a May skirmish, as decades-old tensions over the border territory persist.

The escalation broke the ceasefire brokered in July by Trump who threatened to halt trade talks with the two countries unless they ended the fight.