According to Ukrinform, Ukrainian President Volodymyr Zelensky stated this in a video address.
"Today, President Putin announced a special military operation in Donbas. Russia has carried out strikes on our military infrastructure and on our border guards, border detachments. Explosions were heard in many cities of Ukraine. We are imposing martial law on all territories of our state. A minute ago, I had a conversation with President Biden. The United States has already begun to mobilize international support. Today, what is needed from you is calm. Stay at home if possible. We work, the army works, the whole security sector of Ukraine works. I, the National Security and Defense Council and the Cabinet of Ministers of Ukraine will be in constant contact with you," Zelensky said.
He noted that he will soon get in touch with Ukrainian citizens again