The appearance of a United States nuclear-powered submarine near the Philippines violates a Philippines' law banning nuclear weapons and is escalating the country's territorial row with China, said Filipino citizens and analysts.

The docking of a US submarine in a Philippine port led to a student protest near the US embassy in Manila on Thursday. The USS North Carolina docked in Subic Bay, north of Manila, on Tuesday. Subic Bay is close to Huangyan Island. The protesters are calling on the US to keep away from the area. [Photo by Jay Directo / Agence France-Presse]??

The Bagong Alyansang Makabayan, a Filipino nationalist group also known as Bayan, said in a statement that the presence of the USS North Carolina in the country's waters may be a violation of a provision of the Philippines Constitution.

"The Philippines is de facto hosting US warships presumably armed with nuclear and other weapons of mass destruction. The entry of the nuclear submarine may be in contravention of the Philippines constitutional ban on nuclear weapons," Bayan Secretary-General Renato Reyes was quoted by Gulf News as saying.

"Article II, Section 8 of the Philippines Constitution states that the Philippines, consistent with the national interest, adopts and pursues a policy of freedom from nuclear weapons in its territory."

Reyes said the submarine, one of the world's most stealthy and advanced, "is directed at all countries in the region but most especially China, in order to keep China subservient to US diktats", according to GMA News.

However, Philippines Navy spokesman Lieutenant Colonel Omar Tonsay was cited as saying the submarines' presence in the country is part of "routine ship replenishment" of supplies.

Reyes also warned that the visit may create a "host of social and legal issues" including possible prostitution and even rape by visiting troops, GMA reported.

The US nuclear-powered submarine docked at a former US Navy base in Subic, which is just 120 nautical miles (222 kilometer) away from Huangyan Island, over which both China and the Philippines claim sovereignty.

The maritime dispute over Huangyan Island blew up after a Philippines Navy ship last month accosted four Chinese vessels which were operating in the island waters. China says it has held the island as part of its territory for centuries.

The visit of the nuclear-powered vessel marks a strategic threat to China rather than a concrete tactic, said Xu Liping, an expert on Asia-Pacific studies with the Chinese Academy of Social Sciences.

"The visit shows America's clandestine support for the Philippines on the issue despite the US saying it takes no stance on territorial claims", said Xu.

"What the US does is more important than what it says. China should alert to the issue."

We cannot ignore the anti-US voices in the Philippines and the country's pro-American policies are against ASEAN's idea to balance the ties with different powers around the world, Xu added.

Yang Baoyun, a professor of Asian studies at Peking University, told China Daily that the vessel's visit may not be just because of the recent tension between China and the Philippines; it is also one step in Washington's "return to Asia" strategy.

"If there was no issue over Huangyan Island, the US will still increase its military presence in the Asia-Pacific region...The Huangyan Island issue is accelerating Washington's pace in returning to the region."