Ukrainian President Volodymyr Zelenskyy said Friday his country had been "left alone" to fight Russia after the Kremlin announced a "special military operation" in the Donbas region.  

"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."

He said he had contacted 27 leaders of European countries, and none of them had directly responded to Ukraine's request to join NATO. "Who is ready to give Ukraine a guarantee of NATO membership? Everyone is afraid." 

Zelenskyy, who remains in Ukraine, said Russian "sabotage groups" had entered the capital Kyiv and he was the "target number one." 

"They want to destroy Ukraine politically by taking down the head of state," he said.

But he added he's not afraid of negotiations with Moscow on issues including Ukraine's neutral status and security guarantees.

Russian President Vladimir Putin on Thursday authorized a "special military operation" in the Donbas region, but Ukraine confirmed that military targets across the country were under attack. Putin said the operation aims for "demilitarization and denazification of Ukraine." 

Further expansion of NATO and its use of Ukraine's territory is unacceptable, Putin said, adding that Russia cannot tolerate threats coming from Ukraine. 

Zelenskyy said 137 Ukrainian soldiers were killed Thursday on the first day of fighting. He signed a decree ordering a general mobilization, following an earlier decision to sever ties with Moscow.

The United States and its NATO allies announced a range of sanctions on Russia over the latest escalation. They have provided military aid to Kyiv but refused to send troops into Ukraine. 

The Pentagon on Thursday ordered the deployment of an additional 7,000 troops to Germany, but President Joe Biden reiterated that he will not send U.S. troops to fight in Ukraine. 

"Our forces are not and will not be engaged in the conflict with Russia in Ukraine," Biden said in an address from the White House. "Our forces are not going to Europe to fight in Ukraine, but to defend our NATO allies."

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