Russia's foreign ministry has told an international organisation set up to verify a ban on nuclear tests that a military testing accident in northern Russia earlier this month is none of its business and handing over radiation data is entirely voluntary.

Key points: Five nuclear workers were killed in the explosion on August 8, with three others injured

Five nuclear workers were killed in the explosion on August 8, with three others injured The explosion caused a spike it radiation levels in nearby towns

The explosion caused a spike it radiation levels in nearby towns Russia has accused the United States of stroking military tensions by testing a ground-launched cruise missile

The Vienna-based Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) said on Monday (local time) that two Russian monitoring sites closest to the mysterious explosion went offline days after the blast, soon followed by two more, fuelling suspicions that Russia had tampered with them.

Russia's state nuclear agency, Rosatom, has acknowledged that nuclear workers were killed in the explosion on August 8, with three others injured in the blast involving "isotope power sources", which occurred during a rocket engine test near the White Sea in far northern Russia.

The Interfax news agency on Tuesday cited Deputy Russian Foreign Minister Sergei Ryabkov as saying his country's transmission of data from radiation stations to the CTBTO was voluntary and that the August 8 accident was not a matter for the CTBTO.

The explosion caused a spike in radiation in a nearby city and prompted a local run on iodine, which is used to reduce the effects of radiation exposure.

Russian authorities have given no official explanation for why the blast triggered the rise in radiation.

US-based nuclear experts have said they suspect Russia was testing a nuclear-powered cruise missile vaunted by President Vladimir Putin last year.

The CTBTO's International Monitoring System includes atmospheric sensors that pick up so-called radionuclide particles wafting through the air.

Lassina Zerbo, head of the Comprehensive Nuclear-Test-Ban Treaty Organisation, said data from stations on or near the path of a potential plume of gas from the explosion were still being analysed.

Putin says no risk of increased radiation levels

But Mr Putin said on Monday there was no risk of increased radiation levels after the blast earlier this month.

Speaking alongside French President Emmanuel Macron ahead of bilateral talks on Ukraine and Russia's relationship with the European Union, Mr Putin said that all of those injured and killed in the blast would receive state awards.

He also said that all necessary safety measures were being taken and that there was no radiation risk.

Russian President Vladimir Putin says there is no increased radiation risk. ( AP: Alexander Zemlianichenko )

Mr Putin was speaking at Mr Macron's summer residence in southern France ahead of talks on a range of subjects between the two leaders.

The bilateral talks saw the leaders disagree on issues including the ongoing conflict in Russia, and the crackdown of opposition protests.

Russia accuses US of stoking tensions with cruise missile test

Russia accused the United States on Tuesday of stoking military tensions by testing a ground-launched cruise missile, but said it would not be drawn into an arms race, TASS news agency reported.

The Pentagon said on Monday it had tested a conventionally configured cruise missile that hit its target after more than 500 kilometres (310 miles) of flight, its first such operation since the demise of a landmark Cold War-era nuclear pact this month.

The United States formally withdrew from the Intermediate-Range Nuclear Forces Treaty (INF) with Russia on August 2 after accusing Moscow of violating the pact, a charge dismissed by the Kremlin.

The US missile test would have been prohibited under the treaty.

"All this elicits regret, the United States has obviously taken the course of escalating military tensions. We will not succumb to provocations," Russian Deputy Foreign Minister was quoted as saying.

"We won't allow ourselves to be pulled into a costly arms race."

The INF banned land-based missiles with a range of between 500-5,500km, reducing the ability of both countries to launch a nuclear strike at short notice.

Thousands of Russians paid tributes to the five killed nuclear workers at the August 12 funerals. ( AP: Russian State Atomic Energy Corporation ROSATOM )

Mr Ryabkov said that despite the test, Russia did not plan to deploy any new missiles, unless the United States did so first.

China also expressed concern.

In Beijing, Chinese Foreign Ministry spokesman Geng Shuang said the test showed the United States was stoking a new arms race and confrontation, which would have a serious negative impact on regional and global security.

"We advise the US side to abandon outdated notions of Cold War thinking and zero-sum games, and exercise restraint in developing arms," Mr Geng told a daily news briefing.

Reuters/AP