KRAMATORSK, Ukraine 

At least five Russian aircraft and one helicopter were shot down, Ukraine's Command of Joint Forces announced on Thursday.

"On Feb. 24, 5 aircraft and an aggressor helicopter were shot down near the area of the Joint Forces," the command said on Facebook.

"The Joint Forces give a worthy rebuff to the armed forces of the Russian Federation," said the statement.

Noting that Ukraine's military units are keeping their positions, the command said "the enemy suffers losses."

"Keep calm and believe in Ukrainian defenders. Let's win together!" it concluded.

Ukrainian President Volodymyr Zelenskyy Thursday announced martial law across the country as Russian troops entered the border and hit targets around the capital Kyiv.

"Explosions were heard in many cities of Ukraine. We are declaring martial law across the country," Zelenskyy said.

According to reports a wounded woman was seen as Russian airstrike damaged an apartment complex outside the northeast Kharkiv city.

Russia is targeting key areas in cities with weapons and missiles, according to reports.

On early Thursday, explosions were reported in several Ukrainian provinces, including Kyiv, and several tanks reportedly crossed the border with Belarus into Ukraine.

In a statement on Thursday morning, the Russian Defense Ministry announced it is using “high-precision weapons” to disable air defense systems, military airports, and air forces in Ukraine.