President Ferdinand Marcos Jr. said on Monday the presence of a Russian attack submarine in the Philippines' exclusive economic zone (EEZ) in the South China Sea was "very worrisome". "That's very concerning.

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.

A Russian submarine's presence in the Philippine EEZ sparks concern. President Ferdinand Marcos Jr. called it 'very worrisome'. Russia claims it was exercising navigation rights under international law,