The Security Service of Ukraine (SBU) has no confirmed information about the involvement of Russian special services in the assassination attempt on the participants of the anti-terrorist operation (ATO), Adam Osmayev and Amin Okuyev, deputy chief of the SBU branch in Kyiv and Kyiv region Pavlo Daniukov has said.

"At the moment, we have no such confirmed data," Daniukov said at a briefing in Kyiv on Friday answering a question about the possible involvement of Russian special services in the attempted murder.

He added that if they receive any definite information on the involvement of Russian special services or lack thereof, they will make it public.

As reported, two members of the Kyiv-2 police battalion, who participated in the ATO in Donbas, the spouses, Adam Osmayev and Amina Okuyeva, were attacked in the Podil area of Kyiv on June 1.

It is believed that the assailant, who introduced himself as a foreign journalist, had arranged for a meeting with the couple beforehand.

"When they got into the car, the man took out a Glock pistol from a box and shot Osmayev in the chest. In response Amina fired several shots with her Makarov pistol into the gunman," the police said.

Both Osmayev and the killer are now in hospital with serious gunshot wounds. As of Friday morning, Osmayev's condition is grave but stable.

Anton Gerashchenko, an advisor to the Ukrainian interior minister, said later that the killer was found in possession of a Ukrainian identification document in the name of Oleksandr Dakar, born 1958.

The police are considering the couple's "patriotic position" as the key line of inquiry.

In 2012 Osmayev was detained in Odesa by Ukrainian law enforcement officers on suspicion of staging an explosion in an Odesa apartment. Investigators also suspected that he and his accomplice had been planning to assassinate Russian President Vladimir Putin.

In September 2013 a second defendant in the case, Ilya Pyanzin, was sentenced to ten years of imprisonment in Russia after being extradited from Ukraine.

The European Court of Human Rights recommended Ukraine not to extradite Osmayev to Russia and Ukraine decided to suspend his extradition. Osmayev was released from custody on November 19, 2014 after two and a half years in jail.

In February 2015, after the death of Isa Munayev, a commander of the so-called Dzhokhar Dudayev international peacekeeping battalion fighting on the side of the Ukrainian army in Donbas, Osmayev became the battalion's new commander.