South Korea's President Park Geun-hye called North Korea's development of a submarine-launched ballistic missile a "serious challenge," warning "stern retaliation" against North Korea if provoked.

The President on Tuesday called on officials to maintain strong deterrence in cooperation with the United States over North Korea's provocative acts, presidential spokesman Min Kyung-wook said in a written briefing, reported by the official Yonhap news agency.

About 28,500 U.S. troops are stationed in South Korea as deterrence against North Korea.

Park made the comment in a rare meeting of top security officials to discuss North Korea's recent test-firing of a submarine-launched ballistic missile (SLBM).

The participants included Park's security adviser, the spy chief, the defense minister, the foreign minister and South Korea's point man on North Korea, Min said.

The meeting, the first in a year, came three days after North Korea claimed that leader Kim Jong-un oversaw a successful underwater test-launching of a "strategic submarine ballistic missile." "North Korea's development of a submarine-launched ballistic missile is a serious challenge that undermines stability on the Korean Peninsula and in Northeast Asia," Park said, noting Pyongyang is banned from any ballistic missile activity under U.N. resolutions.

Her comments came days after North Korea threatened to fire without warning on South Korean naval vessels it accused of violating its territorial waters.