The conflict has killed hundreds of thousands of people directly or indirectly and left millions on the brink of famine, according to the UN which calls it the world's worst humanitarian catastrophe.
The renewed pressure comes as the pandemic further shakes the North’s economy, which was already battered by crippling US-led sanctions over its nuclear weapons programme and decades of mismanagement by its own government.
Western leaders warned Russia not to consider shifting a country's national borders by force, highlighting that Moscow would pay a high political and economic price for any military intervention in Ukraine.
Huge explosions lit up the sky early on Sunday south of the capital, Kyiv, where people hunkered down in homes, underground garages and subway stations in anticipation of a full-scale assault by Russian forces.
South Korea's Joint Chiefs of Staff reported that North Korea had fired a suspected ballistic missile toward the sea off its east coast from a location near Sunan, where Pyongyang's international airport is located.
One short-range ballistic missile crossed the Northern Limit Line, the de facto maritime border between the two countries, prompting a rare warning for residents on the island of Ulleungdo to seek shelter in bunkers.
Talks with North Korea should not be for political show but contribute to establishing peace, South Korean President Yoon Suk-yeol said on Wednesday, just hours after the North test fired two cruise missiles into the sea.
Viewing the drills as a military threat, North Korea decided to stage "the simulation of an actual war” to check and improve its war deterrence and send a warning to its enemies, KCNA said.
The launch comes after the navies of South Korea, the United States and Japan staged trilateral anti-submarine exercises on Friday for the first time in five years, and follows a visit by US Vice President Kamala Harris to the region this week.