MOSCOW, February 7 (RAPSI) - A criminal case was initiated after an explosion rocked Trade Union House in Kiev, the current base of operations of the pro-Eurozone protesters, acting head of Kiev police Valery Mazan told the reporters on Thursday.

Earlier, it was reported that a box exploded in the Trade Union House, leaving two men injured. An investigative team then tried to enter the building to survey the crime scene, but an opposition lawmaker who intorduced himself as tje quartermaster, told the investigators that the protesters decided to blovk them from entering the building.

Kiev and other Ukrainian cities have been rocked by mass anti-government street protests since President Viktor Yanukovych backed away from signing a series of agreements with the EU in November in favor of cementing ties with Russia.

Among the protesters’ main demands is a return to the previous version of the constitution enacted in 2004 by then-President Viktor Yushchenko. The amended version, under which some presidential powers were handed over to the parliament and government, was ruled unconstitutional in 2010 during the first year of Yanukovych’s presidency.