Russia has closed part of the White Sea to shipping today after a mysterious explosion at a military base which killed two people and caused a radiation spike.

A rocket engine exploded at a ballistic missile test site near the village of Nyonoksa earlier on Thursday, injuring at least four people in addition to the two dead.

Moscow initially insisted radiation levels were normal but later a nearby city's local authority acknowledged a spike.

The blast has been shrouded in mystery and it is unclear why Russia would respond by closing part of the White Sea, which it has shut to commercial shipping for a month.

The explosion occurred during testing of a liquid propellant jet engine at a military base, killing two and injuring four

The explosion at the Russian missile testing site took place near the village of Nyonoksa in Arkhangelsk today (pictured)

Radiation leak causes 'mass hysteria' There was 'mass hysteria because of the radiation rumours' reported a local radio station in Severodvinsk. This led to 'spikes in vodka and white wine sales,' said Ekho Severa. And iodine-containing medicines had sold out in in local pharmacies after a rush by residents. Severodvinsk people were urged to close their windows and not let children go outside, said another report in the city. The radio station urged people to stop seeking so-called remedies for radiation which 'won't work', such as alcohol. But they also highlighted a pocket radiation counter with a normal reading. The Russian health ministry denied any medical concerns among the general population after claims of a radiation spike. 'Civilians and residents of neighbouring populated localities were not hurt,' the ministry said. Ekho Severa also accused the Russian Emergencies Ministry of failing to give clear information on the incident to the media. 'We want to stress that yet again the Ministry of Emergencies press services refuses to communicate with the media,' said one report. 'There are no updates from them.' Advertisement

Local reports say the engine exploded in a barge next to the testing range in Russia's northwestern Archangelsk region.

At least six servicemen and civilian engineers were injured, and two of them later died of injuries.

Other reports said three military personnel were in an 'extremely grave condition' after the explosion caused a fire.

Ksenia Yudina, a spokeswoman for the city authorities, told TASS news agency: 'A short-term rise in background radiation was recorded at 12 o'clock in Severodvinsk.'

City officials said background radiation levels had fully 'normalised'. The population of Severodvinsk was 185,000 at the beginning of 2017, according to officials.

A spokeswoman for authorities in the northern city who said there was a 'short-term spike in radiation levels', according to TASS news agency.

The type of device has not been revealed nor the reason for the explosion.

Russian media said an area near Nyonoksa is used for tests on weapons including ballistic and cruise missiles that are used by the Russian navy.

City officials said background radiation levels are now fully 'normalised'.

Nyonoksa hosts a navy facility that serves as a base for testing intercontinental ballistic missiles intended for nuclear submarines.

Former Northern Fleet command Admiral Vyacheslav Popov said: 'Explosions at test sites are commonplace.

'They should be treated calmly. This was a test.

'A negative result is also a result.

'In order for a missile to fly, you need to test all its components: engines, fuel - everything.'

He forecast the Russian authorities would give scant detail of the incident.

Only those who participated could say what went wrong.

'Yet no one will name all the reasons,' he said.

'This requires an investigation.

'It is not known what kind of explosion, the volume, or scale. There is no such information yet. '

But in an extraordinary move, Dmitry Chistyakov, head of press service of Archangelsk region's Emergencies Ministry, revealed he had been banned from answering media questions on the incident.

He told the media: 'Colleagues, to my deepest personal regret I am banned from commenting the situation in Nyonoksa.

'I have received so many calls and didn't take about 40.'

Russia has closed part of the White Sea to commercial shipping after the mysterious explosion today. Buildings at the military base near Nyonoska are seen in 2011

Admiral Vyacheslav Popov, former commander of the Northern Fleet, said of the test site near Nyonoksa: 'This is a current test site of the Navy, where the test benches are located, including liquid-fuel engines for new sea-based ballistic missiles.

'It was probably during such tests that an explosion occurred.'

The country is particularly sensitive to radiation leaks after the Chernobyl disaster in 1986 which took place in the former Soviet Union in what was the worst nuclear disaster in history.

The defence ministry said: 'During the test of a liquid propellant jet engine, an explosion occurred and the equipment caught fire.

'As a result of the accident, six defence ministry employees and a developer were injured. Two specialists died of their wounds,' it said, adding that radiation levels near the facility were 'normal'.

'There's no radioactive contamination,' a spokeswoman for the Arkhangelsk region, where the base is situated, said earlier.

The accident is the second to hit the Russian military in less than a week, after a fire broke out in an ammunition depot in Siberia on Monday, causing huge explosions.

At least one person was killed and eight injured while thousands had to evacuated from their homes following the blaze at the depot in the Krasnoyarsk region.