Stanislav Yezhov, assistant and interpreter to Ukrainian Prime Minister Volodymyr Groysman, who was detained by Ukraine's SBU Security Service (SBU) this week did not have access to secret information and was under surveillance by the SBU for a long time, PM Groysman has said.

"We knew for months that Yezhov was under suspicion and that he was working for foreign secret services. Thanks to the SBU, he was monitored during this time, of course, with the support of my office. As soon as enough information was gathered, Yezhov was detained," Groysman said during question time in Ukraine's Verkhovna Rada on Friday.

According to the prime minister, Yezhov was not privy to state secrets.

"The SBU operation against Yezhov took months, and there were no information leaks. This shows there are many honest SBU agents and operatives in our counter-intelligence services," Groysman said.

Yezhov will be arraigned by Kyiv's Shevchenkivsky District court at 15.00 on Friday.

SBU agents detained Yezhov on December 20. He is suspected of state treason, pursuant to Part 1 of Article 111 of Ukraine's Criminal Code.

SBU agents say Yezhov collected information on behalf of Russia.