KIEV, July 6 (Xinhua) -- At least three Ukrainian servicemen were killed and nine others injured in a mortar explosion at a military facility in northwestern Ukraine early Friday, the Defense Ministry said.

The accident occurred around 05:55 a.m. local time (GMT 0255) at the Rivne combined-arms range during live-fire tactical exercises, the ministry said.

Military practices at the facility have been suspended.

Ukrainian Prime Minister Volodymyr Groysman tweeted that a probe will be launched to investigate the circumstances of the blast. According to preliminary information, the incident happened due to safety rules not being followed.

It was the second such blast in a military facility in less than two years. In 2016, a serviceman was killed and eight others were injured in a mortar explosion at the Shyroky Lan training range in the southern Mykolaiv region.