The Security Service of Ukraine (SBU) on Thursday said that they broke an armed rebellious group active in major cities of the war torn country.
A special forces official and a Russian member of the rebellious group died during the shootout.
SBU detained five members of the group, two of them Russian, following the operation.
"Just in one place in the capital we found eight homemade explosive devices, four kilogrammes of TNT, automatic weapons, about 40 hand grenades and 2,000 cartridges," the SBU spokeswoman Olena Gitlyanska said.
The conflict in the country broke out in April 2014 after the Russian annexation of Crimea, as separatists backed by Russia took control of most parts of the Donetsk and Luhansk regions of eastern Ukraine.
Kiev has repeatedly accused Moscow of attempting to destabilise Ukraine aside from supporting the pro-Russian separatists.
The UN High Commissioner for Human Rights released a report on Wednesday stating that arms and fighters are still pouring into eastern Ukraine from Russia, and the death toll has risen to over 9,100.
"There remains, however, an inflow of ammunition, weaponry and fighters from the Russian Federation into the territories controlled by the armed groups, leaving the situation highly flammable," the report said.