Ukraine's SBU Security Service tried to disrupt the undercover operation of the National Anti-corruption Bureau of Ukraine (NABU) involving the State Migration Service of Ukraine (SMS), as well as unmask the bureau's agent network, NABU Director Artem Sytnyk has said.

"The primary task of the SBU was to disrupt the concrete operation aimed at documenting the corrupt scheme of the SMS… We cannot finish the operation now. We can only analyze the collected information. The second goal was to disrupt all operations conducted by NABU agents undercover. This goal was also achieved. All operations have been terminated," Sytnyk said during a press conference on Friday, December 1.

The NABU director called SBU actions "simply amoral."

"The third goal was to receive information about the NABU agent network. It was not achieved, because they did not receive information about this network, despite the searches and holding our agents incommunicado for 30 hours and ruining equipment," Sytnyk said, adding that SBU agents also tried to intimidate bureau employees.

"We have a small team – 700 persons, but with moral qualities necessary for resisting such attacks," Sytnyk said.