No casualties were reported at the depot 176 kilometres east of the capital of Kyiv.
Ukraine's state security service said it was investigating possible sabotage, and the defence ministry's spokesman said the fact that explosions were set off in different parts of the depot pointed to sabotage. Explosions were happening at a rate of two to three a second at one stage, according to the Defence Ministry.
Almost 10,000 people have been evacuated after a fire and a series of explosions hit an ammunition depot located some 180 kilometers east of Kyiv, Ukrainian authorities say. Meanwhile, explosions could also be heard in a nearby wood where some ammunition appeared to have come down.
The fire and explosions began at around 3:30 a.m. local time at the Defense Ministry's depot No. 6, which is spread over about 700 hectares, a statement said.
Authorities closed airspace in a 30-kilometre radius and suspended road and rail transport.
He said: "Two simultaneous explosions, and after five minutes two more explosions in another part of the depot suggest it was military sabotage". "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 has ordered an urgent report into the explosions.
In March a year ago, a massive explosion and fire at a munitions depot near the central Ukrainian city of Kharkiv prompted the evacuation of about 20,000 residents living within a 20-kilometer radius of the site.
Moscow denies sending troops and weapons to help separatists in the conflict, but admits that Russian "volunteers" are helping the rebels.