Thailand announced a curfew in its southeastern Trat province on Sunday as fighting with Cambodia spread to coastal areas of a disputed border region, two days after U.S. President and would-be peacemaker Donald Trump said the sides had agreed to stop.

The Southeast Asian neighbours have resorted to arms several times this year since a Cambodian soldier was killed in a May skirmish, reigniting a conflict that has displaced hundreds of thousands of people on both sides of the border.

"Overall, there have been clashes continuously” since Cambodia again reiterated its openness to a ceasefire on Saturday, Thai Defence Ministry spokesman Rear Admiral Surasant Kongsiri told a press conference in Bangkok after announcing the curfew.

Thailand is open to a diplomatic solution but “Cambodia has to cease hostility first before we can negotiate,” he said.

Thai forces on Saturday said they had destroyed a bridge that Cambodia used to deliver heavy weapons and other equipment to the region and launched an operation targeting pre-positioned artillery in Cambodia’s coastal Koh Kong province.Cambodia accused Thailand of striking civilian infrastructure.

Thailand’s curfew covers five districts of Trat province that neighbour Koh Kong, excluding the tourist islands of Koh Chang and Koh Kood. The military had previously imposed a curfew in the eastern Sakeo province, which remains in force.

Thailand and Cambodia have exchanged heavy-weapons fire at multiple points along their 817 kilometre (508 mile) border since Monday, in some of the most intense fighting since a five-day clash in July that ended with Trump and Malaysian mediation.

Trump said he spoke to Thailand’s caretaker Prime Minister Anutin Charnvirakul and Cambodian premier Hun Manet on Friday, and said they had agreed to “cease all shooting”.

On Saturday, Anutin vowed to keep fighting “until we feel no more harm and threats to our land and people”.A White House spokesperson later said Trump expected all parties to honour commitments and that “he will hold anyone accountable as necessary to stop the killing and ensure durable peace”.