Russian President Vladimir Putin has told widows of the five scientists who died in a nuclear explosion earlier this year that their husbands were working on 'the most advanced and unmatched technical' weaponry.

Putin's comments came during a ceremony of state decorations at the Kremlin today where he awarded the deceased employees of Russia's state nuclear company with the Order of Courage, posthumously.

'They led a very difficult, responsible and critical direction, we are talking about the most advanced and unmatched technical ideas and solutions,' he said.

Russia's President Vladimir Putin is pictured today during the ceremony for state decorations, where he awarded the widows of the five dead scientists with the Order of Courage

On August 8, five employees of the Russia's nuclear company, Rosatom, were blown up while testing a nuclear rocket propulsion system. The rescue team is pictured after the tragedy

Vyacheslav Lipshev, 40, was one of the experts killed in the blast. His widow Natalia Alexeeva, 40, posted a tribute: 'I love you my dear, how will I live without you? You are my everything'

On August 8, five employees of the Russia's nuclear company, Rosatom, were blown up while testing a nuclear rocket propulsion system at the Nyonoska testing site in the White Sea. The blast caused a brief radiation spike in the nearby city of Severodvinsk.

Putin said that they made 'an indispensable contribution to the strengthening of the Russian state.'

He expressed his condolences to the widowed but maintained that Russia would go on developing this type of advanced weaponry.

'The fact of possessing such unique technologies is today the most important reliable guarantee of peace on the planet. And no matter what, we will certainly improve this weapon,' he said.

The August explosion raised concerns that a prototype of a weapon, called Burevestnik by Russia and known as Skyfall by NATO, is being developed by the Kremlin.

The daughter of Evgeny Korotaev, 50, a leading electronics engineer, Oksana, 26, posted a childhood picture of her with her father and the caption: 'Daddy, I love you so much'

Experts said they suspected an explosion and radiation release came from an accident during the testing of a nuclear-powered cruise missile at a facility outside the village of Nyonoksa

It has not been confirmed a Burevestnik cruise missile was being tested during the explosion but US experts claim the deadly blast was from a 'Skyfall' rocket

It has not been confirmed whether a Burevestnik cruise 'Doomsday' missile was being tested when the explosion occurred.

But US nuclear experts at the James Martin Center for Nonproliferation Studies in California insist the blast did come from a Skyfall test.

Anne Pellegrino, a research associate at the James Martin Center, told German broadcaster Deutsche Welle: 'Our operating theory is that there was a catastrophic failure of some kind during the testing of Russia's nuclear powered cruise missile. They call it Burevestnik but NATO refers to it as Skyfall.'

Rescue workers of the Arkhangelsk Rescue Service are pictured in training

The mysterious incident led to a 'radiation spike' in the nearby city Severodvinsk, according to reports in the aftermath of the explosion.

Three injured testers are reported to be recovering. They were named for the first time as engineers Dmitry Abanin and Aleksander Manyukhin along with another specialist Sergey Grishin.

The five killed in the explosion were Vyasheslav Yanovsky, 71, one of Russia's most senior nuclear scientists, Vyacheslav Lipshev, 40, director of a secret research institute, Evgeny Korotaev, 50, a leading electronics engineer, Alexey Vyushin, 43, who had developed a high-energy photon spectrometer, and Sergey Pichugin, 45, a testing engineer.