North Korea's propaganda website Uriminzokkiri said in its commentary that the recent drill was a "military provocation that ruins the hard-won peace atmosphere on the Choson peninsula", and that it was an "overt threat" to Pyongyang.
Although North Korea has not gone so far as to renege on its moratorium on nuclear and ICBM tests, which its leader, Kim Jong-un, announced previous year, the Saturday launch indicated that Kim was toying with the idea of lifting the moratorium, analysts said.
It is unclear whether the launch was a test.
People watch a TV news report about the latest North Korean missile launch - the images shown are from an earlier test - at the Seoul Railway Station on Saturday.
The South Korean military said it was conducting joint analysis with the United States of the latest launches. North Korea said last month that it had tested a new type of unspecified "tactical guided weapon", which experts said could be anything from anti-tank weapons to cruise missiles.
Japanese Prime Minister Shinzo Abe has decided not to set any preconditions in seeking talks with North Korean leader Kim Jong Un, government sources said Friday, as Tokyo fears being marginalized by Pyongyang's diplomatic outreach to other countries.
North Korea wanted sanctions relief for partial denuclearization, but the United States refused to relax sanctions without complete denuclearization.
British PM dismisses defense secretary due to security leakage - PM’s office
Labour MP for Wolverhampton South East Pat McFadden, a former Government minister, said: "There are leaks out of the Government". Williamson was to head back to Wolverhampton to join his family, where he was to consider his next steps.
A short-range missile would not violate that self-imposed moratorium.
North Korea had last test-fired the Hwasong-15 intercontinental ballistic missile in late November 2017.
South Korea's liberal president, Moon Jae-in, has doggedly pursued engagement with the North and is seen as a driving force behind the two summits between Trump and Kim.
"Kim wants to ensure the world knows it is upset with the United States hardline stance on denuclearisation and will not bow to external pressure", said Scott Seaman of the Eurasia Group.
ROK Foreign Minister Kang Kyung-wha had telephone talks with U.S. Secretary of State Mike Pompeo concerning the launch shortly after it took place.
But US President Donald Trump later expressed confidence in Kim and the prospect of a nuclear deal. Kim said last month that he would be willing to hold another summit with Trump if the United States changes its hard-line stance on sanctions relief.
But with negotiations lagging, the North appears to be testing the U.S. while staying below that threshold. South Korean officials said they were also looking into the possibility that the projectiles were short-range Scud missiles or rockets from multiple-launch tubes - or both.