KHARKIV, Ukraine - Ukrainian police on Saturday freed the remaining hostages being held in a post office by an man believed to be strapped with explosives, and arrested the hostage taker after an hours-long standoff in the city of Kharkiv."All hostages freed in Kharkiv. The assailant was arrested," President Petro Poroshenko wrote on Twitter, while Interior Minister Arsen Avakov published a picture of the man, with blood streaming down his face, being held by a policeman.None of the hostages were harmed. A Reuters witness at the scene saw special force police in green camouflage rushing to the entrance of the post office, a yellow-and-white building at a road junction in the northeastern city near the Russian border.In earlier statements, police said the man had entered the post office wearing a mask and taken 11 people hostage with the intention of robbing the place. Five of the hostages -- three women and two children -- were released early.