SBU Spokesperson Maryna Ostapenko told a briefing at the Antiterrorist Center, a Ukrinform correspondent reports.
"There is information about the arrival of 150 Cossacks from Crimea to help Sloviansk separatists," Ostapenko has said.
According to her, the activity of pro-Russian forces testifies to their disposition to further destabilization of the situation in eastern regions of Ukraine.
"Activity of pro-Russian forces is not reduced, and the situation remains to be aggravated. Separatists intensify activities aimed at further destabilization of the situation in the East of Ukraine," the SBU Spokesperson noted.
However, Ostapenko assured, the Antiterrorist Center forces demonstrate coherence of their actions: "There is redeployment of major forces of the Antiterrorist Center, filtration measures are enhanced on the border to prevent the militants to the territory of Ukraine from the Russian Federation."
As the SBU Spokesperson said, measures were taken to repel a possible assault at the location of internal troops in Donetsk, a scheme of defense and mining of Druzhkivka, Sloviansk and Kramatorsk streets was exposed, subversive separatist groups were identified in the villages of Makarivka, Chervony Lyman and the city of Luhansk, and plans of the militants were foiled to capture soldiers of the Ukrainian Armed Forces near the village of Karpivka.
"Kramatorsk (except for the downtown) is under control of the Antiterrorist Center. In Sloviansk and Kramatorsk the separatists continue to hold the buildings of the Interior Ministry department, SBU and executive committees. In Chervony Lyman, the formation of armed separatist groups is observed, numbering up to 100 people," Ostapenko said.