Russia has told international nuclear test ban monitors that it does not have to share information on the blast that caused a brief spike in radiation levels in Arkhangelsk region, bolstering speculation that Russia may have tampered with monitoring stations that failed to transmit scientific data after the accident.

Two Russian-operated monitoring stations for the comprehensive nuclear test ban treaty ceased transmitting data two days after the 8 August blast, when a projected radioactive plume from the deadly accident would be expected to reach them.

The data could have given additional information on the amount and kind of nuclear materials being used in the Russian military tests, indicating the level of danger to local residents and the nature of the Russian testing, including whether a small nuclear reactor was involved.

The treaty’s mandate “does not cover development of any types of weapons”, said the deputy foreign minister, Sergei Ryabkov, on Tuesday when asked about why the stations had suddenly gone silent. The decision to transmit data is “strictly voluntary”, he added.

On Monday, the Wall Street Journal reported another two monitoring stations had also suddenly gone offline, bringing the total to four.

Lassina Zerbo, the executive secretary of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), wrote earlier this week that the agency was analysing the “potential plume from the explosion” and was “addressing technical problems experienced at two neighbouring stations”.

A spokesperson for the CTBTO said that the organisation “started experiencing problems with two radionuclide stations – Dubna and Kirov – on the morning of 10 August.” The stations reported “communication and network issues” and apparently had not been restored to full functionality as of Tuesday evening.

The spokesperson also confirmed problems at the Bilibino and Zalesovo radionuclide stations beginning on 13 August.

Russia’s atomic agency has said that five of its employees were killed during a test involving a liquid-fuelled rocket and “isotope power sources” at a military testing range.

Some analysts have said Russia could have been testing an experimental cruise missile that carries a nuclear reactor on board, although other theories have been suggested. They include a nuclear-powered cooling system for liquid-fuelled rockets or other hypersonic or nuclear-powered missile projects.

Q&A What is the 9M730 Burevestnik missile? Show The Burevestnik (Storm Petrel) experimental cruise missile – called "Skyfall" by Nato – is an ambitious nuclear-powered cruise missile in development by Russia's armed forces. The concept builds on an idea originally examined by the US in the late 1950s: a nuclear-powered missile able to fly vast distances powered by an on-board reactor, tracing a complex flight path to outflank enemy defences. Essentially the idea has been to develop a missile with effectively no limitation of conventional fuel range, which could fly around the globe multiple times or trace a flight path – for instance – over the Pacific and through South America to target the US via Mexican airspace, making conventional anti-missile defences, as they are currently deployed, redundant. The US air defence network is configured on the assumption any air attack would come from the north, west, or east, but not the south. By comparison the US Tomahawk cruise missile has a range of 1500 miles. Dismissed by the US decades ago because of the dangers and technical problems involved, the missile has been pursued by Russia in the last few years along with other vehicles designed to outfox conventional defences including high-speed underwater drones and hypersonic glide vehicles. According to what little is known about the project, the missile is designed to be launched using a traditional jet propulsion motor before the nuclear power plant takes over in the air. While it would be a formidable weapon if successfully deployed, leapfrogging US missile capabilities, doubts remain among researchers as to whether its core technology is viable. Peter Beaumont

The comprehensive test ban treaty, signed in 1996, prohibits civilian and military experiments involving nuclear explosions. It is not in force because it has not been signed or ratified by a number of countries, including the US, but Russia has set up monitoring stations that transmit data to the organisation headed by Zerbo in Vienna, Austria.

This month’s blast is not believed to have been caused by a nuclear reaction, but by the ignition of rocket fuel being used in the experiment.

The CTBTO receives information from approximately 300 stations around the world that identify nuclear testing by providing seismic, hydroacoustic and other data. The monitoring stations at Dubna and Kirov, which ceased transmitting data on 10 August, monitor radionuclide particles in the air.

On Tuesday, Dmitry Peskov, the Kremlin spokesman, said that president Vladimir Putin, was receiving updates about the situation in Severodvinsk, where gamma radiation exceeded the normal level by 16 times after the explosion on 8 August.

But Peskov said of the test stations: “I don’t know what those stations are, and what data they transmit,” he said. “It is outside of our purview.”