At least five people were killed in the Ukrainian government offensive in the eastern city of Slovyansk on Friday, pro-Russian activists said.
Stella Khorosheva, a spokeswoman for the pro-Russian militants, said two civilains and three militants were killed during the operation.
In the southern city of Odessa, at least three people were killed and many injured during clashes between security forces and pro-Russian militants, according to Ukraine's Interior Ministry.
Separately, in a written statement, interim President Oleksandr Turchynov said many separatists were killed, wounded and arrested during the government offensives.
'Anti-terror' operations against armed pro-Russian groups in the east of the country were not going as quickly as hoped, Turchynov said.
He said all rebel-held checkpoints around the city were captured by Ukrainian security forces during the course of Friday's operation.
Government buildings and police stations in several eastern Ukraine cities are in the hands of armed pro-Russian groups. A prosecutor’s office building in Donetsk was the latest building seized on Thursday by groups that support Russia.
Kiev has accused Russia for the occupation of buildings while Russia denies the accusations.
"We demand that Russia cease the provocations against our country and that it stop using terrorism, sabotage, and military threats as forms of pressure on our country," Turchynov said.
Earlier on Friday, pro-Russian separatists shot down two Ukrainian helicopters, killing a pilot and serviceman in Slovyansk.
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