Russian President Vladimir Putin has announced a military operation in Ukraine even as Ukraine reported multiple explosions in many cities.

 

Putin warned other countries that any attempt to interfere with the Russian action would lead to “consequences they have never seen.” 

 

As Putin spoke, big explosions were heard in Kyiv, Kharkiv and other areas of Ukraine. Later, air sirens went off in Kyiv, indicating that the city is under attack.

 

Ukraine President Volodymyr Zelenskiy said Russia had carried out missile strikes on Ukrainian infrastructure and the country's border guards.

 

Ukraine’s Minister of Foreign Affairs said that the country will defend itself from Putin’s “war of aggression.” Ukraine will defend itself and will win, said the minister. 

 

Ukraine's Interior Ministry has said Russia's "invasion has begun" with missile strikes on Kyiv. CNN reporters and witnesses in cities across Ukraine have also reported hearing explosions.

 

Ukraine's President introduced martial law across the country on Thursday, urging citizens to remain calm. 

 

Ukraine was attacked through multiple borders, the Ukrainian state border service said. "At about 5:00 am, the state border of Ukraine in the area with the Russian Federation and the Republic of Belarus was attacked by Russian troops supported by Belarus," the service said. 

 

It added that border guards, along with Ukraine's Armed Forces and National Guard, are "firing at the enemy" depending on the situation on the border.

 

US President Joe Biden said he has spoken with his Ukrainian counterpart, Volodymyr Zelensky, and briefed him on the steps he is taking "to rally international condemnation".

 

In a statement, Biden says he condemned the attack as "unprovoked and unjustified".

 

The US president says he will be meeting with G7 leaders on Thursday, and the US and allies "will be imposing severe sanctions on Russia".

 

"We will continue to provide support and assistance to Ukraine and the Ukrainian people," he says.