Philippine activists and political groups are planning to hold anti-Chinese protests in Manila Friday amid a simmering standoff over a disputed island chain in the South China Sea.

China has issued a safety warning to its citizens in the Philippines because of the protests, and is calling on Manila to ensure that the demonstrations remain peaceful.

The dispute began over a month ago when Chinese surveillance vessels prevented a Philippine warship from arresting Chinese fishermen near the contested Scarborough Shoal.

Both sides have used increasingly heated language in the conflict, with Chinese state media on Thursday even hinting at the possibility of war.

But a Friday editorial in the Communist Party-affiliated Global Times appeared to dial back the rhetoric, saying “cool heads must prevail.”

China has indicated there will be economic consequences for what it views as “provocative” and “groundless” claims to the island by the Philippines.

Most of China's travel agencies have suspended trips to the Philippines. And the official China Daily said Friday that shipments of fruit from the Philippines will now be subject to stricter inspections, saying that much of its imports are piling up at Chinese border docks.

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 says the shoal is within its internationally recognized exclusive economic zone.

China has already rejected a request by the Philippines to refer the issue to an international court.

The standoff is part of a wider territorial dispute in the South China Sea, parts of which are also claimed by Vietnam, Taiwan, Malaysia, and Brunei. China claims nearly the entire region, which is thought to contain large amounts of oil and natural gas.

To ease tensions, the Association of Southeast Asian Nations has been negotiating details on a code of conduct in the South China Sea. The deadline for reaching an agreement is July 2012.