An aerial view of the mouth of the Scarborough Shoal
An aerial view of the mouth of the Scarborough Shoal AFP

Philippine President Ferdinand Marcos on Sunday condemned what he called "illegal and reckless" actions by China's air force last week against a Filipino military plane patrolling over a disputed South China Sea reef.

Two Chinese air force aircraft undertook a "dangerous manoeuvre" and dropped flares in the path of a Philippine air force turboprop over Scarborough Shoal on Thursday, according to the Philippine military.

Manila said the Chinese actions put the lives of its crew in danger, but that the patrol plane returned safely to base.

The Chinese actions were "unjustified, illegal and reckless, especially as the PAF (Philippine Air Force) aircraft was undertaking a routine maritime security operation in Philippine sovereign airspace," Marcos said in a statement.

Marcos "strongly condemns" the incident, the statement said, adding it was "worrying that there could be instability in our airspace".

China defended its operations on Saturday, saying it had "organised naval and air forces to lawfully... (drive) away" the Philippine plane, following "repeated warnings".

"We sternly warn the Philippines to immediately stop its infringement, provocation, distortion and hype," said a statement from the Southern Theater Command of the People's Liberation Army, adding that "China has indisputable sovereignty over Huangyan Island (Scarborough Shoal) and adjacent waters".

The incident follows a series of increasingly tense confrontations 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 on Thursday came a day after China carried out a combat patrol near Scarborough Shoal to test the "strike capabilities" of its troops.

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.

Despite last week's incident, the Philippines said Sunday it will continue to patrol its Exclusive Economic Zone, defined by the United Nations Convention on the Law of the Sea as waters beyond a coastal nation's territorial seas over which it has sovereign rights to explore and exploit natural resources.

"The Armed Forces of the Philippines reaffirm our determination to conduct regular surveillance operations in line with international law," military spokesperson Francel Padilla said in an interview over local radio station DZBB.

"We will safeguard our country's sovereignty and security over our maritime domain," she added.