The Security Service of Ukraine (SBU) has made a report on the measures, which have been taken by the Ukrainian military men as a part of the counter-terrorism operation, adding that pro-Russian activists continue to destabilize the situation in east Ukraine.

"The activity of the pro-Russian forces doesn't drop, the situation still is tense. The separatists intensify activity meant for the further destabilization of the situation in the region," Security Service spokeswoman Maryna Ostapenko said at a press briefing in Kyiv on Monday.

She said the main forces involved in the counter-terrorism operation "reinforce measures on the state border not to let Russian militants enter the Ukrainian territory and to prevent assault of the interior troops in Donetsk."

Information about "disclosure of the nest of the snipers in the residential areas of Horlivka, Semenivka and Sloviansk (Donetsk region), weapon ambush around the hotel complex "Tsarytsyne", health center "Shakhtobudivnyk" and hospital in Sloviansk" is being verified.

The SBU spokeswoman reported about disclosure of the scheme of defense and mining of the streets in Sloviansk, Kramtorsk and the village of Druzhkivka, revealing of the subversive separatist groups near the city of Luhansk, the village of Makarivka and the town of Krasny Lyman.

"The plans of the militants to take soldiers of the Armed Forces of Ukraine hostage near the village of Karpivka have been frustrated. Capture of the administrative buildings in Horlivka, the attack on the units of the National Guard, blocking of the columns of the Armed Forces near Kramatorsk, attack on the armored personal carrier units of the anti-terrorist subdivisions in Sloviansk and Krasny Lyman have been prevented," Ostapenko said.

Besides, Kramatorsk, in addition to its center, is under control of the counter-terrorism center, while pro-Russian activists still capturing police departments, security services and city executive committees in Sloviansk and Kramatorsk.

"There are formations of the armed groups of the separatists with a total up to 100 persons in [the town of] Krasny Lyman. There is also information about arrival of 150 Cossacks from Crimea to Sloviansk to help separatists," she said.

Ostapenko reminded that early on May 3, due to the special operation, the armed sniper nest of the militants in the town of Kostiantynivka that was based on the TV aerial has been defused. There are injured among the Alfa special police force fighters, she reported.