North Korea fired multiple artillery shots into a maritime border zone after, South Korea said on Friday.
This comes a day after the South and the US announced their decision to extend their 5-day joint military exercises which had started on Monday.
According to South Korea's military, the North fired more than 80 artillery rounds into the sea.
“The irresponsible decision of the US and South Korea is shoving the present situation caused by provocative military acts of the allied forces to an uncontrollable phase," said Pak Jong-chon, secretary of the Central Committee of the Workers' Party of Korea, further warning that, the extension of the military exercises "is a very dangerous and wrong choice."
In past days, North Korea and South Korea have exchanged missile fires that landed off the coasts of the two neighbors for the first time amid heightened tensions over the joint military exercises by Washington and Seoul.
Pyongyang demands the large-scale joint military exercises be stopped, insisting that the drills are a rehearsal for an invasion of the North.
“[M]ilitary rashness and provocation can be no longer tolerated,” it warned.
North Korea also fired a suspected intercontinental ballistic missile (ICBM) and two short-range missiles toward the East Sea, claimed the South's military, triggering evacuation alerts for residents in parts of central and northern Japan.
South Korea's Joint Chiefs of Staff (JCS) said in a statement that it had detected what was presumed to be an ICBM launch from the Sunan area in Pyongyang at around 7:40 am local time and the firing of two apparent short-range ballistic missiles from Kaechon in South Pyongan Province from around 8:39 am local time on Thursday.
The statement, cited by South Korea's official Yonhap news agency, added that if the launch of an ICBM, a presumed Hwasong-17, was confirmed, it would mark the first firing of such a missile by Pyongyang since late May.
Despite the initial warnings claiming the ICBM flew over Japan, Tokyo later said that it was a false alarm.