North Korea on Thursday issued a 48-hour ultimatum for South Korea to dismantle loudspeakers blasting propaganda messages across the border or face military action, Seoul's defence ministry said.
The message from the Korean People's Army general staff was delivered through an inter-Korean military hotline, the ministry said in a statement.
The 48-hour period will expire at 5:00pm (0800) on Saturday.
The warning was delivered after North Korea fired a rocket across the border, prompting South Korea artillery units to retaliate with dozens of 155mm howitzer shells.
Cross-border tensions have been elevated for weeks following mine blasts that maimed two members of a South Korean border patrol earlier this month and the launch Monday of a major South Korea-US military exercise that infuriated Pyongyang.