Ukrainian Prime Minister Yulia Tymoshenko rushed to the east of the country Monday after an explosion in a hospital killed seven people, according to the regional administration.

The explosion in the eastern town of Luhansk was caused by oxygen tanks which blew up in a cardiac ward at the hospital.

The Luhansk region's administration said in a statement rescue teams had recovered four more bodies from under the rubble, on top of the three deaths already confirmed by local officials.

A local official said earlier that 22 people -- 14 doctors and eight patients -- were in the vicinity of the explosion and rescue workers and the police were checking how many were missing under the rubble.

"At the time of the explosion in the hospital, there was a shift change and at the moment no one knows where all the doctors are," a spokesman for Luhansk's regional administration told Reuters.

Tymoshenko came second behind opposition leader Viktor Yanukovich in a presidential election Sunday and the two face off in a second round vote on February 7.