The Armed Forces of the Philippines (AFP) monitored the presence of a Russian submarine in the West Philippine Sea (WPS) for the "first time," a high-ranking navy official said on Monday.

Philippine Navy spokesperson for the WPS, Rear Admiral Roy Vincent Trinidad, confirmed that a Russian submarine, identified as UFA 490, was sighted 80 nautical miles west of Cape Calavite, Occidental Mindoro, on 28 November.

“This is the first time we detected it, were able to respond, and track it,” he said.

“Upon receiving the report, the Philippine Navy immediately deployed assets to monitor and address the situation, ensuring the security of Philippine waters.”

Trinidad noted there was “friendly” communication between the Philippine Navy and the crew of the Russian submarine when it entered the country’s exclusive economic zone (EEZ).

The Navy's BRP Jose Rizal (FF150) established radio communications with the submarine, confirming its identity, crew complement, and navigational intent.

In response to the radio challenge, the Russian vessel stated it was awaiting improved weather conditions before proceeding to Vladivostok, Russia.

Trinidad said Philippine naval forces, including the FF150, escorted and monitored the submarine to ensure compliance with maritime regulations within the Philippine EEZ.

“We were surprised when we detected it, but we responded immediately. We were able to establish communications, and so far, it was okay. We had a friendly exchange of information, and they informed us where they were going,” he stressed.

Further, Trinidad said the submarine’s passage through the Philippine EEZ is “not illegal.”

Citing the United Nations Convention on the Law of the Sea, Trinidad explained that a foreign vessel is authorized to pass through the country’s EEZ under the principle of “freedom of navigation.”

He added that the Russian vessel did not conduct any untoward actions while it was in the WPS.