Some 12,000 people were evacuated after an explosion at the ammunitions depot east of the capital Kiev.
Ukrainian authorities suspect sabotage lay behind explosions that tore through an ammunition depot in the early hours of Tuesday, sending fireballs into the sky and causing more than 12,000 people to be evacuated.
No casualties were reported at the depot, located 176 km (about 110 miles) east of the capital, Kiev. Explosions were happening at a rate of two to three a second at one stage, according to the defence ministry.
Ukraine has in the past pointed the finger at Russia for such types of incidents as relations between the two countries have plunged following Moscow's annexation of Crimea in 2014 and support for separatist forces in the Donbass region.
Without providing evidence, Ukraine's deputy prime minister linked the explosions to a decision pending in Istanbul this week to allow Ukraine to establish an independent national church, which Russia fiercely opposes.
A Reuters witness later saw powerful explosions continuing at the depot. The blasts shattered windows in surrounding village houses while explosions could also be heard in a nearby wood where some ammunition appeared to have come down.
The fact that explosions were set off at intervals in different parts of the depot pointed to sabotage, a defence ministry's spokesman said.
"Two simultaneous explosions, and after five minutes two more explosions (in another part of the depot) suggest it was military sabotage," Defence Ministry spokesman Rodion Tymoshenko said at a press briefing.
Authorities closed airspace in a 30 km radius and suspended road and rail transport. The emergency services reported that gas and electricity supplies to the area had been disrupted.
"The rumble started at 3 a.m. It rumbled three times, then I woke up and ran to my family and started waking them up," said Valentyna Petrenko, a resident in the nearby village of Druzhba.
"We crept into the basement. We took documents, papers, everything we could, blankets, pillows and stayed in the basement."
Hundreds of people and equipment were deployed to the site, a statement by the emergency services said, joined by Prime Minister Volodymyr Groysman and the head of Ukraine's armed forces Viktor Muzhenko. President Petro Poroshenko had called for a report.
Several large fires have hit ammunition and weapons depots in recent years, an additional drain on Ukraine's military. Fighting between Ukrainian troops and Moscow-backed separatist rebels has killed more than 10,000 people since 2014.
Last year, massive explosions at a military depot in the Vynnytsya region, 270 km west of Kiev, forced the authorities to evacuate 24,000 people.