The trouble started after pro-EU protesters forced out the Kremlin-backed government in Kiev, and Russia moved to annex the Crimean peninsula.Here, we have profiled some of the key figures involved on both sides of the growing unrest.Vyacheslav Ponomaryov is the self-proclaimed pro-Russian mayor of Sloviansk, the stronghold of the separatist movement in eastern Ukraine.He is an opponent of the government in Kiev, which he calls a "junta".Mr Ponomaryov is often seen travelling through Sloviansk in a car without a registration plate, accompanied by men armed with machine guns.He was not a well-known figure before the recent unrest, so there is little credible information available about him. It is believed he ran a small soap factory in the region.There are also unconfirmed reports that he fought as a Soviet soldier in Afghanistan in 1980s and has connections to the Russian special forces.Recently he asked Russia President Vladimir Putin to send a Russian peacekeeping mission to eastern Ukraine.Some 40 people, including journalists, including observers from the Organization for Security and Co-operation in Europe and members of Ukraine's security service are being held in Sloviansk.Mr Ponomaryov says he will release them in exchange for separatists detained by the authorities.One of the best-known leaders of the uprising, Igor Strelkov directs armed pro-Russian activists in eastern Ukraine, especially in Sloviansk.The Ukrainian security service says he works for the Russian military intelligence agency, the GRU, and his real name is Igor Girkin. He was born in 1970 and registered in Moscow, according to the service.He was previously active in Crimea. In an interview with Russia's Komsomolskaya Pravda newspaper, Mr Strelkov said that his brigade in Sloviansk had been formed in Crimea from volunteers only, but most of them had combat experience fighting for the Russian armed forces in Chechnya, Central Asia, Yugoslavia, Iraq and even Syria.According to various sources, Mr Strelkov himself also took part in conflicts in Yugoslavia as a volunteer, and in Chechnya under contract.Russian media, however, dismiss any ongoing links with the Russian military - in fact they suggest he is a military enthusiast who specialises in historical re-enactment and staged recreations of battles.They describe him as commander of Sloviansk's self-defence forces, but say he is not a GRU colonel, but rather a retired officer of the Russian Federal Security Service (FSB). His last role before retirement was reportedly with FSB's Directorate for Combating International Terrorism.One of the Ukrainian government's key figures in the east, Serhiy Taruta was appointed governor of the Donetsk region in order to assert its authority and quell the protests in the area.Nevertheless, several towns have been taken over by pro-Russian protesters and armed men in unmarked uniforms.He claims he never wanted to be a state governor. He is one of the founders of the transnational metallurgical corporation ISD.Forbes Ukraine lists him among the wealthiest citizens of the country, estimating his fortune at $697m (£415m, 500m euros).Mr Taruta has been working from one of the business centres of the city, while the Donetsk regional administration building remains occupied by protesters.He says the ousted President Viktor Yanukovych and his close allies, who fled the country in February, play a crucial role in the separatist unrest in eastern Ukraine.He believes their actions are aimed at disrupting the presidential elections scheduled for 25 May 2014.Hennadiy Kernes has been mayor of Kharkiv since 2010.He was shot and critically wounded by an unknown gunman in the city on 28 April 2014.Mr Kernes was originally a supporter of President Yanukovych, but changed his stance in favour of the new government in Kiev after Mr Yanukovych was ousted.He has recently backed the idea of a united Ukraine.The mayor has been described as a "mini-oligarch" - a successful businessman wealthy enough to launch a career in politics.He has been accused of starting his business career as an organised crime boss, a claim he denied while acknowledging that he was once jailed for fraud - a minor offence "partly fabricated" by his enemies, he insisted.He is a close friend of Party of Regions presidential candidate Mikhail Dobkin.(BBC)ANN.Az