He pointed out that the possibility of a provocation by the North is growing amid the political turmoil and leadership vacuum caused by the court ruling to unseat the president.

Pyongyang is feared to make additional provocations during the ongoing joint military exercises between Seoul and Washington, which last through April.

In a separate video conference, Joint Chiefs of Staff Chairman Gen. Lee Sun-jin also demanded most servicemen in the Army, Navy, Air Force and Marine Corps focus on their own duties to protect the people's lives and security against threats from the North, Seoul's JCS said in a statement.

There is no unusual movement in the North Korean military following the court's decision, the military said.

Earlier in the day, the eight justices at the Constitutional Court unanimously ruled to unseat Park, who was impeached by parliament in December over a corruption scandal involving her and her longtime confidante Choi Soon-sil.

In phone talks with Han immediately after the court's unprecedented ruling, Acting President and Prime Minister Hwang Kyo-ahn called for the military's "unwavering" efforts to guard the country against outside threats in times of "national emergency."

Hwang also ordered the military to completely prepare for and respond to any type of provocations especially from North Korea based on its strong alliance and joint military drills currently underway with the US.

On March 1, South Korean and US troops kicked off a two-month exercise, Foal Eagle, involving the ground, air and naval forces of the two allies. They also plan to start a two-week computer-simulated command post exercise, called Key Resolve, on March 13.

The USS Carl Vinson aircraft carrier is scheduled to arrive in Busan around March 15 to participate in the drills. The US Air Force's F-35B stealth fighter will also take part in the ongoing war games to hone its precision ground strike capabilities, according to the ministry.

Pyongyang has long bristled at such maneuvers, denouncing them as a rehearsal for invasion, though the allies have said the drills are aimed at defending against nuclear and missile threats posed by the rogue regime.

North Korea has test-fired five ballistic missiles so far this year after conducting two nuclear tests and 24 missile launches last year. (Yonhap)