At least seven people have died in a blaze at a Russian defense research institute 160 kilometers from Moscow, and more than 20 injured.

Russia's TASS news agency says the country has opened a criminal investigation into fire safety after Thursday's incident. 

"Military investigators will look into the case," TASS quoted a law enforcement source as saying, citing an article of Russia's criminal code on violating fire safety requirements and causing death by negligence.

The fire broke out late Thursday morning in the Russian city of Tver, northwest of Moscow, on Thursday, requiring the evacuation of around 100 people, TASS reported.

An electrical fault caused the fire, which covered 2,500 square metres, Interfax reported on Friday. The local government of the Tver region said the blaze had been extinguished on Friday morning and that 13 people were hospitalized.

Footage from the scene circulating on Russian social media showed thick smoke and flames billowing from the institute's windows. Still images taken late on Thursday evening showed the charred husk of a four-storey building with blackened holes where windows had previously been.

Regional authorities said firefighters had prevented the blaze from spreading to neighboring buildings and houses.

The institute is engaged in aerospace research, including on a unified air defence system for the CIS bloc of former Soviet republics, according to the Russian defence ministry's website.

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There were also unconfirmed reports of a fire at one of Russia's largest chemical plants.

Images on social media, republished on various news websites, seem to show a considerable blaze at the Dmitrievsky chemical plant in Kinsehma, 400 kilometers north-east of Moscow.

The facility is the largest producer of butyl acetate and industrial solvents in eastern Europe and a global supplier of other chemical and petrochemical products.