Chinese naval and air forces conducted patrols around a flashpoint reef in the South China Sea (West Philippine Sea in the Philippines) on Saturday, after a slew of tense encounters with the Philippines in the disputed waterway in recent months.

The patrols coincided with joint exercises carried out by the United States, Australia, Japan, New Zealand and the Philippines in Manila's exclusive economic zone and within the South China Sea.

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

Its claims include the waters around Scarborough Shoal — which Beijing seized from Manila in 2012 — where the Chinese military's Southern Theater Command said Saturday it held air and sea patrols. 

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

Beijing said the training activities around the shoal included "reconnaissance, early warning, and air-sea patrols".

"Certain countries outside the region are stirring up trouble in the South China Sea, creating instability in the region," the Southern Theater Command said in a statement.

"China holds indisputable sovereignty over Huangyan Island and its adjacent waters," it added, using the Chinese name for Scarborough Shoal (Bajo de Masinloc in the Philippines).

Freedom of navigation

Japan's defense ministry said in a statement Saturday that the joint drills involving the five countries took place in the South China Sea. 

Its maritime destroyer Sazanami participated in the exercises, the ministry said.  

In its own statement, the United States said the maritime exercises conducted with its allies demonstrated "a collective commitment to strengthen regional and international cooperation in support of a free and open Indo-Pacific".

Australia's defense department separately confirmed Saturday that the HMAS Sydney and a Royal Australian Air Force P-8A Poseidon maritime patrol aircraft were participating in exercises aimed at "upholding the right to freedom of navigation and overflight".

Tensions between China and the Philippines have flared in the past few months during a series of confrontations in the waters around the contested Second Thomas Shoal and Sabina Shoal.

In July, the two sides said they had reached a provisional deal on resupply missions to a Philippine ship, the Sierra Madre, which is grounded on the Second Thomas Shoal with a garrison on board, aimed at asserting Manila's claims to the reef.

Beijing said Friday it had "supervised" a Philippine ship as it delivered supplies as part of a resupply mission to the grounded vessel at the shoal.