Around 24,000 people have been evacuated after massive explosions and a fire at a military ammunition depot in central Ukraine.
The blasts occurred at a military base near Kalynivka in the Vynnytsya region, 270km west of Kiev, Ukrainian emergencies service said in a statement.
One person was injured, it said.
The area was also closed to rail and road traffic. The national railway company Ukrzaliaznytsya diverted 14 passenger trains.
Arriving in the region hours later, Prime Minister Volodymyr Groysman said "external factors" were behind the incident.
He said the cause of the fire was under investigation.
Olena Gitlyanska, spokeswoman for the Ukrainian Security Service, told the Unian news agency they are treating the fire as sabotage. She didn't provide further details.
Ukraine President Petro Poroshenko called for an urgent meeting of the country's top officials to discuss the situation.
The depot houses some 188,000 tonnes of munitions, including projectiles for various rocket-launch systems.