Huangyan Island, as Scarborough Shoal is known in China, is an inherent part of Chinese territory, Chinese Foreign Ministry spokesman Hong Lei said.
However, China stands ready to find a diplomatic solution to the standoff over the shoal in the South China Sea that has been going on since mid April, said Hong in a report by China's state-run News agency Xinhua.
The shoal is more than 400 miles off the Chinese coast but 150 miles off the coast of Zambales, a province on the western shore of Luzon Island, the largest and most northern Philippines island.
China's claim to the islands rests on interpretations of several treaties beginning with the Treaty of Paris 1898 which Beijing claims never specifically mentioned Scarborough Shoal as Philippines territory.
What makes ownership of Scarborough Shoal important -- as with the other disputed territories in the South China Sea -- is access to natural resources including oil and gas on the seabed and fishing rights in the area.
Beijing claims a Philippines warship is stopping a dozen Chinese fishing vessels from leaving a sheltered harbor within the shoal after their captains sought refuge from rough seas.
The Philippines have claimed only four vessels are within the shoal.
A report this week by Xinhua said "the Chinese people are enraged by the offensive behavior of the Philippines over the Huangyan Island dispute, expressing full support for efforts by the Chinese government for safeguarding its territorial sovereignty."
The Philippines "keeps making trouble in the waters around Huangyan Island, China's indisputable territory," the Xinhua report said.
The report quoted Chinese fishermen saying the island always has been Chinese territory and their families have fished in the area for decades.
He Shixuan, a fisherman in the city of Qionghai in south China's Hainan province and the owner of one of the 12 Chinese fishing vessels "harassed by the Filipino warship," said "we have no reason to be afraid of any country, as we are fishing around our own island, nor do we need to leave the waters."
Also, safety concerns over travel to the Philippines by Chinese nationals have meant a number of Chinese travel agencies have canceled package tours, Xinhua said.
Meanwhile, China's foreign ministry is in talks with North Korean official concerning reports that 29 Chinese fishermen are being held hostage by a group demanding around $190,000 for their release.
The Chinese news Web site Morning Whistle quoted reports from Xinhua saying the three vessels and their crew allegedly were abducted May 8 within Chinese waters off the coast of China's northern coastal city of Dalian.
Beijing officials also have been dealing with another marine territorial dispute, off the coast of Japan.
A report in the South Korean Chosun Ilbo said Chinese negotiators met their Japanese counterparts to discuss overlapping claims to the Diaoyu Islands, which the Japanese call the Senkaku Islands.
As well as Vietnam and China, ownership of various Spratly islands and reefs -- some only visible at low tide -- are disputed by Brunei, Taiwan, Malaysia and the Philippines, although Brunei doesn't occupy any of the islands.
The Spratly dispute has erupted into open military confrontation on occasions, such as the brief 1988 Johnson South Reef skirmish between China and Vietnam in which about 70 Vietnamese military personnel were killed.