In Mindanao, presumed Japanese soldiers left behind from WWII were found living with a rebel group and Japanese officials are investigating.
"The pair, in their 80s, were reportedly found on southern Mindanao island.
The men were expected to travel to meet Japanese officials on Friday, but have yet to make contact.
The claim drew comparisons with the 1974 case of Lieutenant Hiroo Onoda, who was found in the Philippines jungle unaware the war had ended.
'Incredible if true'
The two men on Mindanao contacted a Japanese national who was collecting the remains of war dead on Mindanao, according to government sources.
They had equipment which suggested they were former soldiers.
"It is an incredible story if it is true," Japan's consul general in Manila, Akio Egawa, told the AFP news agency.
"They were found, I believe, in the mountains near General Santos on Mindanao Island.
"At this stage we are not saying either way whether or not these two men are in fact former soldiers. We may be in a better position later today," he said.
According to Japanese media reports, the pair had been living with Muslim rebel groups and at least one of them has married a local woman and had a family.
The BBC's Tokyo correspondent says the likelihood is that they are well aware the war is over but have chosen to stay in the Philippines for their own reasons.
Mindanao has seen more than two decades of Muslim rebellion and many areas are out of central government control.
Japan invaded the Philippines in 1941, shortly after the bombing of Pearl Harbor, and set up a brutal puppet government.
In the closing months of the war, there was heavy fighting with US troops in the mountainous, heavily forested islands.
The Sankei Shimbun daily said the men would most likely be members of the Panther division, 80% of whom were killed or went missing during the final months of the war.
It speculated there could be as many as 40 Japanese soldiers living in similar conditions in the Philippines.
When Lt Onoda was found on the Philippines island of Lubang in 1974, he initially refused to surrender.
Only when his former commanding officer was flown over from Japan did he agree to leave the jungle.
He later emigrated to Brazil."