The Philippine military deployed a navy ship and air force planes to shadow a Russian submarine, which passed through the South China Sea off the country's western coast last week, a security official said Monday. One official said the navy was surprised to see the vessel because it was a "very unique submarine."

The Russian submarine identified itself in response to a Philippine navy two-way radio inquiry, saying it was en route home to Russia's eastern city of Vladivostok after joining an exercise with the Malaysian navy, Jonathan Malaya, assistant director-general of the National Security Council, said.

The submarine, like other foreign ships, has the right of "innocent passage" in the country's exclusive economic zone but it still sparked concern when it was spotted on Thursday about 80 nautical miles off the Philippine province of Mindoro, Malaya said.

Roy Vincent Trinidad, spokesman for the navy in the South China Sea, said the incident is "not alarming."

"But we were surprised because this is a very unique submarine," he told AFP.

The 74-metre (243-foot) long vessel is armed with a missile system that has a range of 12,000 kilometers (7,450 miles), according to Russia's state-run TASS news agency.

The submarine was sighted after it surfaced due to weather-related conditions, Malaya said.

Philippine president says Russian submarine "worrisome"
"All of that is very concerning," President Ferdinand Marcos Jr. told reporters when asked about the submarine. "Any intrusion into the West Philippine Sea, of our EEZ, of our baselines is very worrisome. So, yes, it's just another one."

Marcos used the Philippine name for the South China Sea, where his country plus Vietnam, Malaysia, Indonesia and other coastal states have faced an increasingly aggressive China, which claims the busy waterway virtually in its entirety.

An alarming spike in territorial confrontations, particularly between Chinese and Philippine coast guard and naval forces, starting last year has prompted closer surveillance by the United States and other Western governments of the key global trade route.

The Philippines coast guard said Monday that a Chinese military helicopter flew close to fishing boats manned by Filipinos in a "dangerous act of harassment" last week at Iroquois Reef, a disputed fishing area in the South China Sea.

Two Philippine coast guard patrol ships have been deployed to the area to protect Filipino fishermen, coast guard spokesperson Commodore Jay Tarriela said.

There was no immediate comment from Chinese officials.

As "60 Minutes" reported recently, tensions have escalated precariously in the waters off the western coast of the Philippines where an international tribunal ruled the Philippines has exclusive economic rights. But China claims almost all of the South China Sea, one of the world's most vital waterways through which more than $3 trillion in goods flow each year.

Meanwhile, China and Russia have expanded military and defense ties since Moscow ordered troops into Ukraine nearly three years ago, and joint exercises involving the Russian and Chinese militaries have ramped up recently. Last week, South Korea's military said it scrambled fighter jets as five Chinese and six Russian military planes flew through its air defense zone.

In September, the U.S. military moved about 130 soldiers along with mobile rocket launchers to a desolate island in the Aleutian chain of western Alaska amid a recent increase in Russian military planes and vessels approaching American territory. Eight Russian military planes and four navy vessels, including two submarines, had recently come close to Alaska as Russia and China conducted joint military drills.

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