Ukrainian authorities release video of what appears to show shots being fired at a Ukrainian border patrol plane.

Border guards say the plane came under fire on Sunday while flying near the administrative border with Russian-occupied Crimea.

A spokesman says three crew members were on an observation mission and that no one was hurt.

Russian forces tightened their grip on Crimea Sunday.

The conflict has been bloodless so far, but tensions are mounting.

Breakaway pro-Russian leaders in Crimea's parliament have decided to make the region a part of Russia.

Ukrainian Prime Minister Arseny Yatseniuk says he's fighting for the country's unity:

(SOUNDBITE) (Ukrainian) UKRAINIAN PRIME MINISTER, ARSENY YATSENIUK, SAYING:

"This is our land, our parents and grandparents spilled their blood for this land. We will not give up a single centimeter of Ukrainian land. Let Russia and the Russian president know this."

Rival rallies continue throughout