Russia has not officially addressed Ukraine regarding the detention of two Russian citizens in the Luhansk region, says Ukrainian Security Service chief Valentyn Nalyvaichenko.

"Russia has not conducted any negotiations with us, and we don't need such negotiations. Our investigation is proceeding. Within the framework of an investigation, negotiations imply a request for a court or an investigator, and there should be an answer," Nalyvaichenko said at a news briefing in Kyiv on Wednesday.

"I think both a court and the investigation will have questions for the Russian Federation, including who issued an order, the commander of what unit, what commander, what commander-in-chief, and the entire vertical that issues orders and forces Russian citizens and military servicemen to go to our territory," he added.

The Ukrainian Security Service claims that Capt. Yevgeny Yerofeyev and Sgt. Alexander Alexandrov, who were captured in the vicinity of Schastia, the Luhansk region, on May 16, are "officers of the Chief Intelligence Directorate of the Ministry of Defense of the Russian Federation."

One of the captives was wounded in the arm and the other in the leg. They were moved to the Ukrainian Defense Ministry's Central Clinical Hospital in Kyiv.

On May 19, they were notified that they were charged with terrorism.