The identity of the object remained unclear, the military said, but Yonhap news agency said it was possibly a drone, more than 90 shots were fired in return and it disappeared from radar screens.
North Korea's new intermediate-range ballistic missile was successfully tested on Sunday and should now be "rapidly" mass-produced, Kim Jong-un, the country's supreme leader has said, according to state media.
On Monday, the U.N. Security Council condemned the launch in a statement and called North Korea's behavior highly destabilizing.
That number is an estimate derived from a report, jointly prepared by US and South Korea militaries, that states North Korea could have as many as 900 ballistic missiles in its arsenal, according to the report.
The launch of a Pukguksong-2 solid-fuel missile from a mobile launcher on May 21 may signal a new level of worries for the US, Japan, and South Korea.
"We will make efforts to secure the efficiency of U.N. Security Council resolutions and ensure that Japan's unilateral sanctions will be carried out thoroughly", Chief Cabinet Secretary Yoshihide Suga told a news conference.
Wang was responding to reporters' questions on Monday while in Ivory Coast, according to the statement.
David Wright, an expert on North Korea's missiles and nuclear program with the Union of Concerned Scientists, said the latest missile could have flown farther but was sacked on a "lofted" trajectory, which sends the missile high up so that it will land in the open seas rather than flying over or splashing down near neighboring countries.
Trump scraps Masada visit after Israel nixes chopper landing
Nine hundred and sixty were killed in the mass suicide and only two women and five children were found alive. The Trump administration announced plans for the president to deliver a speech at Masada early this month.
USA and South Korean officials and experts believe the North is several years away from having such a capability.
North Korean media reports shows leader Kim Jong Un observing what appeared to be video relayed back from the warhead on the missile.
South Korea held a National Security Council meeting after the launch, which its Foreign Ministry said "throws cold water" on efforts to ease tensions on the peninsula. The Security Council discussed that provocation in a closed-door meeting May 16.
"It is the United States' hostile policy and its aggressive joint military drills, nuclear threats and military build-up around the Korean peninsula that really aggravates the situation on the Korean peninsula and the region and which compels the DPRK to also up its nuclear deterrence", he said.
The United Nations on Monday called on the Democratic People's Republic of Korea (DPRK) to stop further ballistic missile testing activities.
Attacks blamed on North Korea in 2010 killed 50 South Koreans. In January 2016, South Korea fired warning shots at a suspected drone which turned back.
Following the May 16 Security Council meeting, North Korean Deputy U.N. Ambassador Kim In Ryong called a news conference to protest Security Council sanctions and vowed to continue developing its weapons programs unless the USA changes its policy toward the North.