Six people were killed on Thursday after a blaze broke out at a defence research institute in the Russian city of Tver about 160 km (100 miles) northwest of Moscow, Russian news agencies quoted local authorities as saying.
The authorities said 27 people had been injured. TASS news agency reported, citing emergency services, that at least 10 people were missing.
Footage from the scene circulating on Russian social media showed thick smoke and flames billowing from the institute's windows. There was no official word on what caused the fire.
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.
(Reporting by Reuters)