ANKARA 

Ukraine's President Volodymyr Zelenskyy held a phone call with US President Joe Biden on Friday to discuss strengthening sanctions against Russia and expressed gratitude to his counterpart. 

Zelenskyy said on Twitter that he had discussed "strengthening sanctions, concrete defense assistance and an anti-war coalition," adding that he was grateful to the US for its "strong support" to Ukraine.

Moscow's military intervention in Ukraine entered its second day on Friday, with the latest reports indicating that Russian troops were heading toward the capital Kyiv from several directions.

Russian President Vladimir Putin had ordered the military intervention on Thursday, just days after recognizing two separatist-held enclaves in eastern Ukraine.

He claimed that Moscow had no plan to occupy the neighboring country, but wanted to “demilitarize” and "denazify" Ukraine.

Zelenskyy accused Russia of trying to install a puppet government and said Ukrainians will defend their country against Russian aggression.

Tensions started escalating late last year when Ukraine, the US, and its allies accused Russia of amassing nearly 150,000 troops on the border with Ukraine.

They claimed Russia was preparing to invade its western neighbor, allegations consistently rejected by Moscow.