Russia's forces are attacking Ukraine from three directions.

The invasion by land, air, and sea began after Russian President Vladimir Putin demanded that Ukraine's military lay down its arms in a pre-dawn TV address. According to preliminary reports, Ukrainian civilians and soldiers, as well as Russian troops, were killed.

"Russia has chosen an evil path, but Ukraine is defending itself," President Volodymyr Zelensky tweeted. Ukraine has declared martial law and cut all diplomatic ties with Russia. It states that weapons will be given to anyone who requests them.

Warning sirens blared in Kyiv, Ukraine's capital and home to nearly three million people, as traffic queued to leave the city also crowds sought shelter in metro stations. "We don't know what to do now," one woman named Svetlana told the news. "We're now going to a safe place, and we're hoping to leave safely."

Mark, a 27-year-old sales executive, stated that he was prepared to fight if called up. "We don't have another option," he explained.

Several neighbouring countries have begun to make plans to accept a large number of refugees. Moldova alone reported that over 4,000 people had crossed the border from Ukraine. The invasion on Thursday came after weeks of escalating tensions as Russia massed troops along Ukraine's borders.

The United Kingdom, the European Union, also other Western allies have vowed to impose tough new sanctions on Moscow, but have said they will not send troops.

"These are among Europe's darkest hours since World War II," EU foreign affairs chief Josep Borrell said.

Several dozens of people have been killed, including approximately ten civilians. Six people were killed in an air strike in Brovary, near Kyiv. A man was also killed in shelling outside Kharkiv, a major north-eastern city.

According to a Ukrainian presidential adviser, more than 40 soldiers were killed and many more were injured. Ukraine claimed to have killed 50 Russian troops and shot down six Russian planes, but this has yet to be confirmed.