A series of explosions were heard in Kharkiv on the night of December 20, reports RBC-Ukraine with reference to its correspondent. At least two explosions occurred in the city. The police of the Kharkiv region called not to leave the shelters until the air raid alert was canceled. “Do not leave the shelter until the air raid alarm goes off. Report any enemy shell hits or casualties to the special police line 102,” police officers said. Brigadier General Serhiy Melnyk confirmed that the Russians had launched attacks on the city. “Kharkiv residents should take cover, the enemy is striking,” Meln…