The Philippines has accused China of sending another warship to disputed islands in the South China Sea, amid a continuing standoff in the area.

Philippine foreign affairs spokesman Raul Hernandez said his government plans to ask Chinese officials why they have violated an agreement not to aggravate the situation.

China's most advanced fishing patrol vessel, the Yuzheng 310, arrived Friday in waters off the coast of Scarborough Shoul.

China's official Xinhua news agency reported the vessel will conduct routine patrols in the area to “protect China's sea rights and ensure the safety of Chinese fishermen.”

The 10-day-old standoff began when Chinese surveillance ships prevented a Philippine warship from arresting Chinese fishermen near Scarborough Shoal, an area both sides claim as sovereign territory.

A crowd of people protested in front of the Chinese embassy in Manila Friday against Beijing's territorial claims.

The Philippines has asked China about referring the issue to an international court, arguing the shoal is well within its internationally recognized exclusive economic zone. China rejected that request earlier this week.

China says the islands, known as Huangyan in China, are a key part of Chinese territory and that any Philippine claim to them is baseless.

The Philippines, China, Vietnam, Taiwan, Malaysia and Brunei all have competing claims in the South China Sea. China claims nearly the entire sea. The Philippines says the shoal is part of its territory based on the U.N. Convention on the Law of the Sea.

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