(QHA) - A defence lawyer for the imprisoned Ukrainian opposition leader Yulia Tymoshenko has been detained by police, an opposition MP says, BBC informs. A top lawyer for jailed former Prime Minister Yulia Tymoshenko on Monday was charged with beating his ex-wife, a move supporters see as a possible attempt to derail a landmark agreement with the European Union that hinges on her release. As reported, Serhiy Vlasenko, Tymoshenko's long-time lawyer and ally, was charged with assaulting his former spouse and was being questioned late in the evening, prosecutor Ruslan Demyanyuk told reporters, according to the Interfax news agency. As reported, Tymoshenko, one of the leaders of the 2004 Orange Revolution, is being treated under prison guard for a back injury. Meanwhile, Ukraine has stopped importing Russian gas, officials say. Gas has been a thorny issue at the heart of Ukrainian politics for years. Tymoshenko was given her seven-year jail term for abuse of power in 2011 over a controversial gas deal with Russia - a conviction she sees as politically-motivated. The EU is urging her release as a condition for signing a big trade deal.