The Ukrainian military claimed on Thursday to have downed five Russian planes and a helicopter in the east of the country near a rebel-held enclave.
"According to the Joint Forces Command, today, February 24, in the area of the Joint Forces operation, five planes and a helicopter of the aggressors were shot down," the army general staff said.
Russian President Vladimir Putin launched a military operation in Ukraine on Thursday with explosions heard across the country and its foreign minister warning a "full-scale invasion" was underway.
Weeks of intense diplomacy and the imposition of Western sanctions on Russia failed to deter Putin, who had massed between 150,000 and 200,000 troops along the borders of Ukraine.
"I have made the decision of a military operation," Putin said in a surprise television announcement that triggered immediate condemnation from US President Joe Biden and other Western leaders, and sent global financial markets into turmoil.
Shortly after the announcement, explosions were heard in Ukraine's capital, Kyiv, and several other cities, according to AFP correspondents.
Ukrainian border guards reported being under attack along the Russian and Belarusian frontiers.
Ukraine's President Volodymyr Zelensky declared martial law and said Russia was attacking his country's "military infrastructure", but urged citizens not to panic and vowed victory.
His foreign minister said the worst-case scenario was playing out.
"Putin has just launched a full-scale invasion of Ukraine. Peaceful Ukrainian cities are under strikes," Dmytro Kuleba tweeted.
"This is a war of aggression. Ukraine will defend itself and will win. The world can and must stop Putin. The time to act is now."
Within a few hours of Putin's speech, Russia's defence ministry said it had neutralised Ukrainian military airbases and its air defence systems.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
