Local residents who live near the airport just outside Donetsk take shelter in a basement. This comes as Ukraine's military said Monday it pulled its forces back from defending the airport -- the latest in a string of reverses for Ukrainian forces fighting pro-Russian separatists.

At a military academy in Kiev, Ukrainian President Petro Poroshenko says Russia's direct involvement in Kiev's war against the separatists had tipped the balance on the battlefield.

(SOUNDBITE) (Ukrainian) UKRAINIAN PRESIDENT, PETRO POROSHENKO, SAYING:

"Direct and open aggression has been launched against Ukraine from a neighboring state. This has changed the situation in the zone of conflict in a radical way and raises new and more difficult questions for our security bodies."

In turn, Russian President Vladimir Putin is pointing the finger at Kiev's leadership for refusing to enter into direct political talks with the separatists.

Putin also says he hopes "common sense" would