Unidentified people have attacked a van of the Ukrainian Security Service during an action on Europe Square in Kyiv on Monday, the service told Interfax-Ukraine.

"Officers of the Ukrainian Security Service who, in line with their duties, were on a mission to expose radio channels through which explosive devices in crowded areas may have been controlled were in the vehicle," the press service of Ukraine's security agency said in a statement.

Security officers always take such actions as part of ensuring security against terrorist threats during mass actions, the statement reads. "Trespassers impudently and cynically seized equipment and damaged the vehicle. They also inflicted bodily harm to officers of the Ukrainian Security Service in the line of their duty," it reads.

The attackers used tear gas, the press service stressed.

"The aforementioned actions were committed with the involvement of some Ukrainian people's deputies," it said.

An Interfax correspondent reported on Monday that demonstrators made an attempt to capsize a van. One of the demonstrators told Interfax-Ukraine that there were weapons in the van and that she sneaked in it but found no arms there.

Meanwhile, Kyiv police reported that a large number of law enforcement officers came to downtown Kyiv after explosive devices were reported to have been found in a van on Triokhsviatylska Street. However, they failed to make their way to the van because of the crowd of demonstrators. Later police drove the van away for an inspection.

According to Svoboda nationalist organization leader Oleh Tiahnybok, demonstrators seized equipment and wire-tapping devices from the Ukrainian Security Service's van in downtown Kyiv.

"We took note of a van that was at the intersection of Europe Square and Triokhsviatylska Street. When demonstrators were passing by this van cellular communication was down," Tiahnybok said on the air of the ICTV channel.

The van was disguised with yellow and blue ribbons and a European Union flag, he said. "One could see through the van's window that there were weapons and unknown equipment. They started to call for help by phone," he said.

Minutes later approximately a thousand law enforcement officers tried in vain to encircle the van, he said.

"We managed to take several suitcases, computers and other equipment from the van. When we opened them, we saw horrible things: special wire-taping equipment, special antennas for catching signals and five pairs of ID plates for the car," Tiahnybok said.