Russian forces are stepping up their offensive in an attempt to besiege the Ukrainian capital, Kyiv.

A Russian military official said on Saturday that their troops struck military airfields and facilities around the city. Russian contingents are reportedly closing in from three directions.

Russian forces continue to press attacks on civilian and other facilities in the second largest city of Kharkiv in the northeast, the strategic port city Mariupol in the east and other areas.

Attacks have also been expanded to the south of Kyiv.

Ukraine's public broadcaster said six missiles struck around a military airfield, about 30 kilometers south-southwest of the capital, and fuel tanks at an ammunition dump there went up in flames.

Civilian casualties continue to rise as the Russian invasion escalates.

The Ukrainian intelligence agency said Friday that Russian troops attacked civilians evacuating by car near Kyiv, killing seven people, including one child.

The United Nations human rights office said at least 579 civilians, including 42 children, had died in the armed attacks as of Friday.

Ukraine's President Volodymyr Zelenskyy said at a news conference on Saturday that roughly 1,300 Ukrainian troops have died since the Russian invasion began.

He reiterated his determination to never surrender, insisting that victory is the only choice for Ukraine, if the country and its people are to continue to survive.