ARKHANGELSK, August 9./TASS/. Medics assess the condition of three people injured during an explosion at a military test site near Severodvinsk, Russia’s Arkhangelsk Region, as grave, though their injuries are not life-threatening, a source in the regional emergencies services told TASS on Friday.

"Three people are in grave condition, but the injuries of the military and civilian specialists are not life-threatening," the source said.

The explosion at a military test site occurred on Thursday, when a liquid propellant jet engine was being tested, the Russian Defence Ministry reported earlier. According to the ministry, the radiation level remained normal after the emergency and there were no hazardous escapes into the atmosphere.

A brief rise of the radiation level above the natural background was registered in Severodvinsk on Thursday following the explosion, the city’s authorities said.

Two were killed and six others injured, the ministry reported.