Groysman said Ukrainian authorities were "doing their best" on Wednesday to minimize the munitions blaze near Vinnytsia, some 200 kilometers (124 miles) south of Kyiv. Ukrainian prosecutors also called the explosions and ensuing fire an act of "sabotage."
Officials said 24,000 residents of villages within five kilometers of the depot were evacuated, a 50-kilometer no-fly zone was in force, and adjacent road and rail traffic had been halted.
Fourteen passenger trains had been diverted.
Stored at the depot — one of Ukraine's largest — near the town of Kalynivka are reportedly 188,000 tons of munitions, including projectiles for various rocket-launched systems.
"This is the arsenal of the Ukrainian army, and I think it was no accident that it was destroyed," Groysman said in televised remarks from the site of the blaze.
Ukraine's military said the fire, the second major incident affecting one of its depots this year, broke out late Tuesday evening, local time, prompting inquiries into whether it was caused by sabotage or negligence.
Artillery shells had exploded one after the other, said the news outlet Pravda, quoting police spokesman Yaroslav Trakalo.
Distant from eastern front
Vinnytsia lies far from eastern Ukraine where Kyiv's troops have fought pro-Russian separatist rebels since 2014 in a conflict that has left 10,000 people dead.
The Russian news agency TASS said some 1,200 firefighters were deployed.
Vinnytsia itself was not in danger, said the city's administration.
Last March, explosions over several days rocked an arms depot near Ukraine's eastern town of Balakliya in the province of Kharkiv which borders Russia. One person was killed.
At that time, authorities pointed the finger at Moscow and separatists, positing that that fire was triggered by explosives dropped from a drone.
ipj/sms (dpa, AFP, Reuters)