KYIV, Ukraine -- Ukrainian President Volodymyr Zelenskyy urged supporters Saturday to speak out in defense of new U.S. sanctions against Russia, hours after President Donald Trump signed an executive order pausing a sweeping package of restrictions targeting the Russian economy.

The White House decision has further raised fears that Ukraine could be left exposed to Moscow's escalating assaults with winter approaching.

Russian attacks overnight killed at least four people, including an ambulance driver, and wounded dozens, officials said.