North Korea has apparently been conducting nuclear operation training, as per Reuters reporting that has cited North Korea's KCNA news agency reporting this on Monday. 

the nation fired two ballistic missiles early on Sunday, authorities in neighbouring countries said, the seventh such launch by Pyongyang in recent days that added to widespread alarm in Washington and its allies in Tokyo and Seoul.

Officials in the South Korean capital have said the uptick in the North’s missile launches could signal it is closer than ever to resuming nuclear testing for the first time since 2017, with preparations observed at its test site for months.

Sunday’s missiles reached an altitude of 100 km (60 miles) and covered 350 km (218 miles), Japan’s state minister of defence, Toshiro Ino, told reporters.

The first was fired at about 1:47 a.m. (1647 GMT) and the second some six minutes later.

The US, Japan and South Korea conducted their own military drills in response.

This escalation of Pyongyang’s missile tests has prompted immediate backlash from Tokyo and has put markets on risk-off alert.