Two China air force aircraft "executed a dangerous manoeuvre at around 9:00am and dropped flares in the path of our NC-212i," armed forces chief General Romeo Brawner said in a statement, recounting the alleged incident Thursday "over" Scarborough Shoal.

He said the Chinese action "endangered the lives of our personnel undertaking maritime security operations," adding that the pilot and crew were unharmed and "safely returned" to a northern Philippines air base.

China defended its operations on Saturday, saying it had "organised naval and air forces to lawfully... (drive) away" the Philippine plane, following "repeated warnings", according to a statement by the Southern Theater Command of the People's Liberation Army.

The statement did not say what specific actions China took, describing its operations as "professional, standard, legitimate and legal".

"We sternly warn the Philippines to immediately stop its infringement, provocation, distortion and hype," the statement said, adding that "China has indisputable sovereignty over Huangyan Island (Scarborough Shoal) and adjacent waters".

The incident is the latest in an increasingly tense confrontation between Manila and Beijing, which claims most of the South China Sea and seized the shoal after a 2012 standoff with the Philippines.

In June, the Philippine military said one of its sailors lost a thumb in a confrontation off Second Thomas Shoal, in another area of the South China Sea, when the Chinese coastguard also confiscated or destroyed Philippine equipment including guns.

Beijing has blamed the escalation on Manila and maintains its actions to protect its claims are legal and proportional.

Following the Second Thomas Shoal clash, the two countries agreed on a "provisional arrangement" for resupplying Filipino troops based on a decrepit warship grounded atop the reef, and also to increase the number of communication lines to resolve disputes in the waterway.

The Chinese air force action Thursday took place a day after China carried out a combat patrol near the flashpoint reef to test the "strike capabilities" of its troops.

- 'Provocative actions' -

Beijing claims almost the entire South China Sea, brushing off rival claims of several Southeast Asian countries, including the Philippines, and an international ruling that its assertion has no legal basis.

Scarborough Shoal, a triangular chain of reefs and rocks, is 240 kilometres (150 miles) west of the Philippines' main island of Luzon and nearly 900 kilometres from the nearest major Chinese land mass of Hainan.

Brawner said the Philippine military "strongly condemns the dangerous and provocative actions of the People's Liberation Army Air Force that endangered the lives of our personnel undertaking maritime security operations recently within Philippine maritime zones".

"The incident posed a threat to Philippine Air Force aircraft and its crew, interfered with lawful flight operations in airspace within Philippine sovereignty and jurisdiction, and contravened international law and regulations governing safety of aviation," he added.

A Philippine military spokesman told AFP the Chinese aircraft involved in the incident were "MRF", an abbreviation for multi-role fighter jets.

The Indonesia-built NC-212i is a multi-role turboprop plane designed for maritime surveillance, troop transport, medical evacuation and "special mission", according to the manufacturer's website.