Philippine navy frigate Jose Rizal established radio contact with the Russian submarine, which confirmed its identity as UFA 490 and its intent. "The Russian vessel stated it was awaiting improved weather conditions before proceeding to Vladivostok, Russia," Trinidad said, without elaborating on why it was in the area.

Tensions between Russia and the Philippines escalated as the Philippine military deployed a navy ship and air force planes to shadow a Russian submarine in the South China Sea last week, security officials said.

Philippine President Ferdinand Marcos on Monday described as "very worrisome" the presence of a Russian attack submarine off the country's coast in the disputed South China Sea.