Russian troops launched their anticipated attack on Ukraine on Thursday, as President Vladimir Putin cast aside international condemnation and sanctions, warning other countries that any attempt to interfere would lead to “consequences you have never seen.”

Ukrainian President Volodymyr Zelenskyy introduced martial law, saying Russia has targeted Ukraine’s military infrastructure and explosions are heard across the country.

Zelenskyy said he had just talked to President Joe Biden and the U.S. was rallying international support for Ukraine.

He urged Ukrainians to stay home and not to panic.