Russia-Ukraine updates: US to ban Russian carriers from its airspace

Russia-backed separatists in eastern Ukraine's Donbas region claimed Thursday that their forces are taking over Ukrainian government-controlled territories amid a Russian invasion.

Ivan Filiponenko, a representative of the military department of the self-proclaimed Luhansk People's Republic, said in a statement that militia units have begun "artillery preparation and an operation to liberate the temporarily occupied territories."

Meanwhile, Eduard Basurin, a spokesman for the militia of the self-proclaimed Donetsk People's Republic, told Russia's Interfax news agency that "forces are delivering strikes on positions of the Ukrainian Armed Forces along the entire line of contact, using all weapons that are available to them."

Separatist leaders want to control all of the Luhansk and Donetsk regions in Donbas. But they currently only have about a third, with the rest controlled by Ukraine.

-ABC News' Tanya Stukalova

Russia claimed Thursday to have neutralized some of Ukraine's military infrastructure amid an attack on the country.

"The military infrastructure of air bases of Ukraine's Armed Forces has been rendered inoperable," the Russian Ministry of Defense said in a statement. "Air defense systems of the Ukrainian Armed Forces have been suppressed."

The Russian defense ministry further alleged that Ukrainian forces on the border "are offering no resistance to Russian units."

Meanwhile, a statement from the Ukrainian Ministry of Defense claimed that five Russian planes and a helicopter had been shot down.

"Reports of foreign media on a Russian aircraft allegedly downed on the Ukrainian territory have nothing to do with the reality," the Russian defense ministry said Thursday.

ABC News could not independently verify the claims on either side.

-ABC News' Tanya Stukalova

In a new security alert, the State Department said it has suspended its consular operations in Lviv in western Ukraine amid “reports of Russian attacks on targets in a number of major Ukrainian cities, including Kyiv, Kharkiv, Odesa, Mariupol and others.”

The U.S. Embassy in Kyiv previously suspended operations on Feb. 12.

“The U.S. government will not be able to evacuate U.S. citizens from Ukraine,” the warning stated.

The State Department advised U.S. citizens to shelter in place and issued instructions on actions to take if a loud explosion is heard or if sirens are activated.

“Further Russian military action can occur at any time without warning. U.S. citizens throughout Ukraine are strongly encouraged to remain vigilant and take appropriate steps to increase their security awareness,” the warning read. “Know the location of your closest shelter or protected space. In the event of mortar and/or rocket fire, follow the instructions from local authorities and seek shelter immediately. If you feel that your current location is no longer safe, you should carefully assess the potential risks involved in moving to a different location.”

-ABC News’ Conor Finnegan

Ukraine’s border service said Russian and Belarusian troops are now attacking from Belarus.

Ukraine’s border came under attack from artillery, tanks and small arms around 5 a.m. local time from Russian troops “with the support of Belarus,” the border service said in a statement.

The attack is happening along much of Ukraine’s northeast border, including the Chernigiv and Zhitomirsky regions that are directly north of Kyiv.

There are reports of casualties.