A Thai F-16 jet has bombed targets in Cambodia, as a simmering border dispute and diplomatic meltdown rapidly ignited into fierce clashes, bombing and shelling that have killed at least 11 civilians and a soldier in Thailand, writes Al Jazeera.

Thailand and Cambodia blamed each other for the new outbreak of fighting that erupted early on Thursday in an area near the disputed Ta Moan Thom Temple, located in a border area in northwestern Cambodia`s Oddar Meanchey province.

Fighting then spread to at least six areas along the border, Thai military official Rear Admiral Surasant Kongsiri said, leading Thailand`s military to close the border between the countries.

Amid regional calls for mediation, Thailand`s caretaker Prime Minister Phumtham Wechayachai told a news conference that fighting had to stop before there could be any negotiations. He said there had been no declaration of war and that the fighting was not spreading to other provinces.

Thailand`s Health Minister Somsak Thepsuthin said 11 civilians, including an 8-year-old boy, and a soldier had been killed in artillery shelling by Cambodian forces. He said 24 civilians and seven military personnel had been wounded.

A Thai military statement detailing the casualties said six civilians had been killed and two wounded in shelling near a petrol station in Ban Phue, Kantharalak district, Sisaket province, about 20km from the border.

The fighting has led to the evacuation of at least 40,000 civilians from 86 villages near the border to safer locations, a district official in Surin province told the Reuters news agency, as residents fled to bomb shelters built of concrete and fortified with sandbags and car tyres.

Cambodia has made no statement about any casualties on its side. Cambodian Prime Minister Hun Manet has requested an urgent meeting of the United Nations Security Council in response to the violence, saying it "gravely threatened peace in the region".