The Philippines on Thursday stepped up army patrols in the jungles of the southern island of Jolo where al Qaeda-linked Islamist militants are holding two Germans captive and are threatening to kill one of them.
The militants from the Abu Sayyaf group have demanded a 250 million pesos ($5.6 million) ransom and for Germany to stop supporting U.S.-led air strikes in Syria in exchange for the freedom of the German man and woman.
They have threatened to behead the man on Friday.
Colonel Allan Arrojado, commander of army units on Jolo, told reporters he was ordering more patrols.
"We are ready for all-out law enforcement operations," he said.
"We will do everything not to endanger their lives," he said of the hostages.
The German man said in a radio interview on Wednesday that he was being held in a hole in the ground which he had been told would be his grave if the rebels' demands were not met.
Abu Rami, a spokesman for the militant group, said they would execute the man at 3 p.m. (0700 GMT) on Friday after giving both the Philippines and Germany enough time to meet their demands.
The militants sent a video to a radio station this week showing a group of men manhandling a handcuffed man who was apparently the captured German.
The man in the video was moaning and complaining that his handcuffs were tight as armed men made him sit in front of black flag, which appeared to be the flag used by Islamic State militants in Syria and Iraq.
The Abu Sayyaf has in the past released video statements expressing allegiance to the Middle Eastern group.
The rebels want an independent Islamic nation in the south of the mainly Roman Catholic Philippines and have earned a reputation for kidnapping in both the southern Philippines and eastern Malaysia.
