Yoon made the remarks as he convened an annual meeting of the central integrated defence council that brings together the military, government and civil defence entities.
In recent weeks, Pyongyang has ramped up tensions on the Korean peninsula with missile tests and verbal threats against Seoul and Washington, while scrapping its decades-long goal of a peaceful reunification and redefining the South as a separate, enemy state.
Yoon warned that North Korea could stage "numerous provocations" to intervene in the upcoming election and called for a tighter security posture.
South Korea is set to elect new members of parliament on April 10, with 300 seats up for grab.
"The North Korean regime is going through fire and water solely for the sake of maintaining its hereditary totalitarian regime, while blatantly ignoring international law and U.N. Security Council resolutions by trading arms with Russia," Yoon told the meeting.
Russia and North Korea have overseen a series of high-level exchanges since last year amid growing criticism of Pyongyang's role in the Ukraine war by allegedly shipping artillery and missiles to Russia.
Both North Korea and Russia deny the accusation and also the charge that Pyongyang has been receiving advanced technology for developing strategic military capability from Moscow in return.
Yoon called for greater cooperation between his country's military, government, police and private actors, as well as additional measures to prevent possible cyber attacks on national infrastructure, and attempts to disseminate false propaganda.
"Cyber attacks can paralyse national functions and people's daily lives in an instant. Fake news and false propaganda may also cause great chaos in society," he said.
Seoul's defence council meeting this year was specifically designed to examine practical ways of responding under various scenarios to North Korean provocations, including long-range artillery and electromagnetic pulse (EMP) attacks, Yoon's office said.
Lee Jae-myung, leader of the main opposition Democratic Party, which has criticised what it called Yoon's hardline North Korea policy, expressed concerns over a possible armed clash near the border.
He called for restoring inter-Korean hotlines, which the North have not responded to since Yoon took office, and warned Yoon against staging "war games" for political gains.
(Reporting by Hyonhee Shin; Editing by Ed Davies and Christian Schmollinger)
By Hyonhee Shin
