Opposition leaders in Ukraine have issued a 24-hour ultimatum for the government to respond to their demands for political change. Speakers told a crowd of tens of thousands packed into Kiev’s Independence Square that they plan to “go on the attack” unless President Viktor Yanukovych makes concessions. Clashes have escalated this week after government forces attacked several camps housing demonstrators. Yanukovych has faced a number of demands including forging closer ties with the European Union instead of Russia and calling early elections.