Meet the private army controlled by sacked Ukrainian billionaire Igor Kolomoisky

Billionaire banking tycoon Igor Kolomoisky was appointed governor of Dnipropetrovsk Oblast, a region in the east of the country that includes Ukraine's third-largest city, in March last year. He had one job - to prevent the territory from falling into the hands of pro-Moscow rebels.

Although he was a close ally of President Petro Poroshenko's new government in Kiev, they had neither the financial nor military clout to allow him to achieve that aim. As such Kolomoisky decided to build his own private army of volunteers equipped with heavy weaponry and paid for all of this from out of his own pocket.

The recruits for these so-called battalions came from Ukraine, Europe and even the odd American with estimates suggesting Kolomoisky could call on over 20,000 troops and reserves. His Dnipro Battalion, also known as Dnipro-1, includes around 2,000 heavily-armed fighters the unit is reported to have cost the banking billionaire $10 million to set up.

They helped play a key role is halting the advance of the Moscow-backed rebels from their strongholds in the neighbouring Donetsk and Luhansk. However, there have long been doubts over where the troops ultimate loyalties lie - to the government in Ukraine or to their regional paymaster.

The events of the past week, with armed men in masks stormed the headquarters of state-owned oil company UkrTransNafta in the Ukrainian capital Kiev following the sacking of its director Oleksander Lazorko, a key ally of Kolomoisky, has only deepened suspicion.

With the governor's sacking on Tuesday by Poroshenko, however, this heavily-armed volunteer force could quickly become a major problem for the Ukrainian authorities.