Under the monument to Soviet state founder Vladimir Lenin, hundreds of pro-Russian protesters gather in Kharkiv.

Some carry signs demanding an end to "fascism".

Others are simply calling for a referendum.

(SOUNDBITE) (Russian) KHARKIV RESIDENT, TATIANA, SAYING:

"People of the southeast demand a referendum. It is the highest form of democracy and we want every voice of every citizen of Ukraine to be heard."

Unlike in other eastern Ukrainian cities, Kharkiv's rally passes without complications.

In Slaviansk, armed separatists have seized government buildings.

The move provoked new warnings from the U.S. who compared the situation to Crimea.

The White House is now calling on Russia to cease efforts to destabilize Ukraine.

Back in Kharkiv, about 5,000 pro-Ukrainian protesters gather to call for unity.

Before marching through the city they carry Ukrainian flags and chant "one united Ukraine."

(SOUNDBITE) (Ukrainian) KHARKIV R