Two Philippine OV-10 planes were flying on Saturday about 1,000 feet over Pugad island when Philippine troops on a nearby island heard a shot ring out, the confidential report obtained by the Agence France Presse said.
The military said it was interpreted as a warning shot.
In his report to Armed Forces chief Gen. Roy Cimatu, Western Command chief Maj. Gen. Manuel Carranza said the OV-10 planes were coming from Palawan when they were shot at with an unknown caliber as they were making their third pass.
The report said the Marines manning a detachment in nearby Parola island also heard the shots. The detachment immediately informed the Naval Station in Pagasa island, which made attempts to contact the aircraft.
During another pass by the planes over the island, another shot was heard, prompting the military commanders to order the planes not to fly over the island again.
The report did not say who fired the shot or if any damage was caused.
Pugad island lies west of the vast Philippine archipelago and is occupied by Vietnam. It is sandwiched by Parola in the north and Pagasa in the south, both occupied by Philippine troops.
Lawmakers last month raised the alarm over the reported invasion by Vietnamese troops of Parola island, but the Armed Forces dismissed the report as a hoax.
The Spratlys is a chain of islands claimed by the Philippines and Vietnam as well as Brunei, China, Taiwan and Malaysia. All claimants but Brunei have troops based on the islands. – AFP, Paolo Romero