The Ukrainian military said Russian or separatist saboteurs blew up a warehouse storing tank ammunition at a military base in the east of the country early on Thursday.

The base, which contained about 138,000 tonnes of ammunition including rockets and tank ammunition, is located in the city of Balakleya about 100 km (60 miles) from the frontline of Ukraine's war against Russian-backed separatists.

Rescue teams were helping residents nearby villages in the eastern Kharkiv region, the military said, and up to 20,000 were evacuated after the suspected drone attack.

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A huge cloud of smoke with fire billows from the site of an ammunition depot of the Ukrainian Armed Forces

A frightening ball of fire erupts in the military base and is felt from nearby residential areas

The sky turns amber as a huge fire caused by multiple explosions fills the air in the Ukraine

A massive plume of smoke rises above the military base as lighter smoke shows debris being flung further afield

A fire reportedly broke out overnight 23 March causing the ammunition at the storage site to detonate

Smoke rises over a warehouse storing tank ammunition at a military base in the town of Balakleya in the Kharkiv region, Ukraine

Ukraine's chief military prosecutor Anatoly Matios said: 'According to preliminary data, as a result of sabotage, last night at 2.46am, fire and explosions caused the detonation of ammunition at several sites storing rockets and artillery weapons.'

Ukrainian Defense Minister Stepan Poltorak said at a briefing that the fire had likely been staged by Russian or separatist saboteurs who probably used a drone.

Poltorak said there was no immediate word on casualties.

The separatist authorities in Donetsk and Luhansk have rejected Poltorak's accusations, arguing in statements carried by the Interfax news agency that the blaze was likely rooted in corruption and incompetence among the Ukrainian military.

There was a fire at the same arsenal in 2015 but the military managed to quickly put it out before munitions started detonating.

Ukraine's chief military prosecutor, Anatolii Matios, also said on Facebook that the blaze was sparked by an act of sabotage and dismissed charges that the fire was an attempt to cover up ammunition theft from the depots, saying it had been protected by nearly 1,000 guards.

The Kharkiv region lies just north of the Donetsk and Luhansk regions, where Ukrainian troops have been fighting Russia-backed separatists.

The conflict has killed more than 9,800 since April 2014.

Ukraine's defense ministry said controls on the border with Russia have been tightened.

Military spokesman Oleksander Motuzyanyk said security around other bases was being beefed up.

Ukrainian Prime Minister Volodymyr Groysman was due to fly to the area later on Thursday, but nobody is thought to have been hurt in the incident.

Saboteurs previously tried to destroy the same base using drones in 2015, another military spokesman, Yuzef Venskovich, told the 112 TV channel.

More than 10,000 people have been killed in the conflict between Ukraine and the separatist rebels since 2014.