Ukrainian President Volodymyr Zelenskyy said 137 were killed Thursday on the first day of fighting as his country faced a large-scale military operation by Russian troops.

He signed a decree ordering a general mobilization, but said his country had been "left alone" to fight its neighbor.  

"We have been left alone to defend our state," Zelenskyy said in a video address. "Who is ready to fight alongside us? I don't see anyone."