Prime Minister Hwang Kyo-ahn is set to hold an emergency National Security Council meeting later in the day, the presidential office said Friday, amid rising speculation that Pyongyang conducted its fifth nuclear test.

Jung Youn-kuk, presidential spokesman, said the meeting will be held at Cheong Wa Dae after a magnitude 5 earthquake was detected at North Korea's nuclear site in the country's northeastern region earlier in the day.

"After being notified of the possibility of a nuclear test, President Park Geun-hye ordered the NSC meeting," another official from the office said.

Park is on an overseas trip and currently staying in Laos, having carried out a series of bilateral and multilateral summits.

"We acknowledge the gravity of the situation and are currently discussing ways to come up with prompt and strong countermeasures," he added.

The premier's office said Hwang has cleared his schedule for the rest of the day.

The meeting will focus on discussing the impact of the possible nuclear test on South Korea's national security as well as international relations. Participants will also share ideas on what actions will be taken at the United Nations.

In January, North Korea conducted a fourth nuclear test after its previous tests in 2006, 2009 and 2013. The Seoul government has yet to confirm the earthquake as a nuclear test.

The previous NSC session as held on Aug. 24 after North Korea fired submarine-launched ballistic missiles. (Yonhap)