REPORT: Troops, tanks and military vehicles entering Ukraine from Belarus

A US defense official told the outlet that it was not clear if the troops were only Russian or also Belarusian.

This followed reports of explosions in multiple cities across Ukraine early Thursday including the capital city of Kyiv, Kharkiv, Kramatorsk, Odesa, and Mariupol during Russia’s invasion of Ukraine.

CNN viewed via a livestream video taken at the Senkivka, the Ukraine crossing with Veselovka, Belarus showing the military column entering Ukraine at approximately 6:48 AM local time.

According to Belarusian state news agency Belta, Russian President Vladimir Putin and Belarusian President Alexander Lukashenko spoke by phone on Thursday.

"At about 5:00 a.m. today, a telephone conversation took place between the Presidents of Belarus and Russia, during which Vladimir Putin informed his Belarusian counterpart about the situation on the border with Ukraine and in the Donbas."

Russia has been massing troops and military vehicles in Belarus near the border with Ukraine for weeks and held joint military exercises.

Meanwhile, Ukrainian President Volodymyr Zelenskyy stated that Ukraine will be imposing martial law in response to the Russian invasion.

"This morning Russia launched a new military operation against our state. This is an unjustified deceitful and cynical invasion."

"There are strikes on military and other important defense facilities, border units are under attack, the situation in the Donbas has degraded. The Armed Forces of Ukraine, all special and law enforcement agencies of the state are on alert. The National Security and Defense Council is working in an emergency mode. Martial law will be imposed."

"Civilians of Ukraine should stay at home. Warn your loved ones about what is happening. Take care of those who need help. All thoughts and prayers are with our soldiers. Glory to Ukraine!"

This is a developing story.