MANILA, Philippines — A Russian attack submarine was spotted in the West Philippine Sea for the first time last week while it was transiting from Malaysia to Russia — a sighting that President Ferdinand Marcos Jr. has flagged as "very concerning."

The Philippine military detected the Kilo-class submarine 80 nautical miles west of Cape Calavite, Occidental Mindoro on November 28. 

The attack submarine was spotted passing through the Philippines' exclusive economic zone (EEZ) after it completed its military exercises with the Malaysian Navy in the Malaysian coastal city of Kota Kinabalu, a Philippine Navy spokesperson told reporters on Monday, December 2. 

"All of that is very concerning. Any intrusion into the West Philippine Sea, of our EEZ (Exclusive Economic Zone), of our baselines is very worrisome," Marcos said in an interview at the sidelines of an event in Marikina City on Monday, December 2.

National Security Council Spokesperson Jonathan Malaya also said the submarine's presence was concerning, prompting Philippine forces to issue a radio challenge to the vessel. 

Russia’s Kilo-class submarines are known for their advanced weaponry and stealth capabilities. Dubbed the “Black Hole” by the U.S. Navy, they are among the world’s quietest submarines, designed for covert operations in coastal waters.

While the detection of the Russian submarine was unexpected, Rear Adm. Roy Vincent Trinidad, the Navy spokesperson for the West Philippine Sea, said the military's response was immediate. 

"This is the first time we've detected, responded to, and tracked a Russian submarine," Trinidad said in mixed English and Filipino.  

"We were surprised that something was detected, but we were able to respond, establish communication, and the conversation went well," he told reporters.

The Philippine Navy deployed its warship BRP Jose Rizal (FF150) and four aircraft to monitor the submarine's movement from November 28 to 29. The BRP Jose Rizal established radio communications with the submarine, which confirmed its identity, crew complement, and navigational intent.

The Russian vessel maintained radio contact throughout its passage and informed Philippine forces that it was "awaiting improved weather conditions before proceeding to Vladivostok, Russia," the Navy official said.

"Philippine naval forces, including FF150, escorted and monitored operations to ensure the submarine’s compliance with maritime regulations within the Philippine Exclusive Economic Zone," Trinidad added.

The Navy spokesperson said the Russian submarine displayed no aggressive behavior and remained surfaced throughout its transit in Philippine waters, with the BRP Jose Rizal maintaining constant surveillance. 

While the submarine's presence raised concerns, Trinidad explained that its passage through Philippine waters was permitted under international law. 

Under the United Nations Convention on the Law of the Sea, foreign vessels may pass through another country's Exclusive Economic Zone (EEZ) because the EEZ grants coastal states rights over resources, not full sovereignty, allowing for freedom of navigation and overflight.

Malaya also explained that while some were worried about the submarine's presence in the Philippine EEZ, the country's maritime zone law clearly states that EEZ rights are primarily economic in nature.

"The EEZ rights are more about economic and natural resources. It's still part of the high seas where any vessel can pass through. This is allowed as long as they're not loitering, extracting natural resources, or conducting unauthorized activities like marine scientific surveys," Malaya said in mixed Filipino and English during a press conference.

Malaya added that the Russian vessel had properly communicated it was only waiting for better weather conditions.

"Similarly, when our own vessels pass through other countries' exclusive economic zones, they are also given the right of freedom of navigation and innocent passage, as long as they don't violate any laws of that country," he added.

As of the latest update from the AFP, the submarine was reported to be moving northward and exiting the Philippine EEZ. 

The Russian submarine's passage through Philippine waters comes amid intensifying naval cooperation between Russia and China in the Pacific region. The two countries declared a "no limits" partnership when Russian President Vladimir Putin visited Beijing in 2022, just days before Moscow launched its invasion of Ukraine. The two countries have since ramped up their joint military activities.

In October, Russian and Chinese navy ships conducted joint patrols in the northeast Pacific Ocean, practicing anti-submarine tactics. Earlier in Julytaya777, both nations held joint naval drills in the waters around Zhanjiang in southern China's Guangdong province. — with reports by Jean Mangaluz

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