Russia has begun mass production of mobile bomb shelters that can protect against a variety of man-made threats and natural disasters, including radiation and shock waves, the emergency ministry's research institute said.

The KUB-M shelter looks like a reinforced shipping container. It can give some protection against radiation, shrapnel, debris and fires and can be deployed in Russia's vast northern permafrost, according to the state institute.

The standard unit accommodates 54 people, and additional modules can be added, the institute said.

The war in Ukraine is entering what some officials say could be its final — most dangerous — phase as Moscow's forces advance at their fastest pace since the early weeks of the conflict in 2022 and the West seeks to shore up Ukraine.

The institute did not link the move to any current crisis, though the announcement came just as President Joe Biden agreed to let Ukraine fire American long-range missiles deep into Russia.

The Kremlin on Monday said Russia would respond to what it called a reckless decision by the Biden administration and cautioned that the move would draw the U.S. directly into the conflict.