At least 18 soldiers were killed and more than 50 others wounded on Saturday in fierce fighting with the armed group Abu Sayyaf and allied fighters on a southern island in the Philippines.
It was the largest single-day combat loss by government forces this year in the restive south, where the military has long battled Muslim separatist rebels and Communist fighters.
Three military officials told the AP news agency the heavy daylong fighting took place on Mindanao island of Basilan. They spoke on condition of anonymity because they were not allowed to publicly discuss details.
Local media reports said about 100 Abu Sayyaf fighters clashed with troops and four soldiers had been decapitated. The evacuation of wounded soldiers was continuing late on Saturday.
In 2015, more than 30 police commandos were killed by Muslim rebels during a government raid on mainland Mindanao.