China on Monday said it was "necessary" to set up a floating barrier at the disputed Scarborough Shoal in the South China Sea, where it has had frequent flare-ups with Philippine forces.

Asked about new satellite images of the barrier blocking the entrance of the shoal's lagoon, Chinese foreign ministry spokeswoman Mao Ning said the shoal, called Huangyan Island in Chinese, was the country's "inherent territory".

"Recently, the Philippine side has taken a series of actions which violate China's sovereignty," Mao said in Beijing.

"China has to take the necessary measures to firmly safeguard our territorial sovereignty and maritime rights and interests."

In a statement on Sunday, the Philippine coastguard accused Chinese coastguard vessels of deploying a floating barrier at the mouth of the lagoon, and conducting "blocking manoeuvres" about 1.3 nautical miles from the shoal last Tuesday during a patrol by a vessel from the Philippine Bureau of Fisheries and Aquatic Resources, which also transported fuel to Filipino fishermen.

Philippine coastguard spokesman Jay Tarriela said Beijing installed barriers "every time" a Philippine government vessel was in the vicinity of the Bajo de Masinloc, the Philippine name for the shoal.

The barrier was removed a few hours after the Philippine vessel left the area, he said.

Commercial satellite images taken on the day also showed the barrier across the shoal mouth, as well as "possible Chinese interception" of the Philippine vessel, according to a Reuters report on Monday.

China's coastguard had said the Philippine government vessel was "driven away" after it had "illegally intruded into" Chinese waters.

Beijing has used a "nine-dash line" to claim almost the entire South China Sea, a claim contested by neighbours including the Philippines, Vietnam, Malaysia, and Brunei.

The Scarborough Shoal, which is rich in fishery and marine resources, has become a flashpoint between Beijing and Manila and a frequent source of diplomatic tension.

The shoal sits within the Philippines' 200-nautical mile exclusive economic zone and used to be part of a shooting range for US military stationed at Subic Bay, while China has claimed it as part of its Zhongsha Islands.

Beijing took control of the shoal in 2012, prompting Manila to take the case to an international arbitration tribunal in The Hague, which ruled in 2016 that China's claims had no legal basis.

China rejected the ruling, but later allowed the Philippines to enter the area when relations improved under former president Rodrigo Duterte.

Since Ferdinand Marcos Jr became president of the Philippines in 2022, tensions have risen again, with frequent reports of confrontations.

Last September, Manila also accused Beijing of installing a floating barrier to stop fishing boats from entering the Scarborough Shoal. It was later removed by the Philippine coastguard in a "special operation".