Beijing has continued to press its claims to almost the entire South China Sea despite an international tribunal ruling that its assertion has no legal basis.

Scarborough Shoal 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.

China in 2012 used coastguard vessels to take control of the shoal, a triangular chain of reefs and rocks that are part of a rich fishing ground and had long been used by Filipino fishermen as a safe harbour.

On Wednesday, the Chinese military's Southern Theater Command said it had "organised a joint combat patrol in the sea and air space" near the area.

The manoeuvres tested "the reconnaissance and early warning, rapid mobility, and joint strike capabilities of theatre troops", Beijing said.

China has long used its coast guard to press its claims in the South China Sea.

And while the Chinese military had been deployed near the Scarborough Shoal in the past, one analyst told AFP Wednesday's action showed they were "becoming more aggressive and forceful".

"It's meant to intimidate," Jay Batongbacal, director of the Manila-based Institute for Maritime Affairs and Law of the Sea, said.

"It's definitely meant to send a message, a show of force," he added.

- 'Aggravate tensions' -

There has been a series of escalating confrontations between Chinese and Philippine vessels in the South China Sea in recent months, including around a warship grounded for years by Manila on the contested Second Thomas Shoal in the Spratly Islands.

One of the most serious incidents took place in June, when Chinese sailors brandishing weapons including knives and an axe boarded Philippine naval vessels near the strategic reef.

The Philippine military said one of its sailors lost a thumb in the confrontation in which Beijing's coast guard also confiscated or destroyed Philippine equipment including guns.

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

In recent weeks, the Philippines and China have agreed on a "provisional arrangement" for resupplying Filipino troops stationed on Second Thomas Shoal and also to increase the number of communication lines to resolve disputes in the waterway.

Last month, the United States said it would provide $500 million in additional military funding to the Philippines to combat Beijing's growing assertiveness.

Beijing said in response that "wooing countries from outside the region to provoke confrontation... will only undermine regional stability and aggravate tensions".

The investment "will only lead to greater insecurity" for Manila, it warned.

Also on Wednesday, the Philippines launched two days of joint sea and air exercises with the United States, Canada and Australia, according to a joint statement.

A Manila military spokesman told AFP that the drills were taking place in the "West Philippine Sea", the country's name for areas it claims in the South China Sea.