President Park Geun-hye on Monday renewed her call for national unity, urging citizens to join forces to ensure "watertight security" in the face of military threats posed by North Korea.

In a video message to a ceremony marking Agent Orange Day, Park also expressed her appreciation to South Korea's Vietnam War veterans, many of whom have suffered from various illnesses due to their exposure to Agent Orange -- one of the defoliants that the U.S. military used to clear jungles and destroy communist forces during the 1960-75 conflict.

"We can make Pyongyang renounce its nuclear program and induce a chance in the country, only through building watertight security by putting together the strength of our people, and enforcing consistent and strict sanctions in tandem with the international community," the president stressed said.

"What matters more than anything else is the united minds of the people," she added.

Commenting on the victims of Agent Orange, the chief executive stressed their sacrifices and dedication have become the "foundation for the development of today's Republic of Korea."

"I hope that all of you, who have contributed to the development of the nation with strong patriotism, can put yourselves at the forefront of the efforts to forge national unity and establish a robust security," she said. (Yonhap)