A series of devastating strikes hit Ukraine’s power and heating infrastructure over the past two days, causing mass blackouts across several eastern regions.

“We expect the quantity of such attacks to grow, and are ready for various scenarios,” senior presidential adviser Mykhailo Podolyak told Reuters.

Podolyak added that Ukrainians should be prepared for problems with power and heat this winter. The east European country often sees temperatures as low as -15 degree Celsius in the cold months.

“Ukraine is expecting its difficult moment from the moment it regained its independence [in 1991],” Podolyak told Reuters.

Podolyak said Ukraine had been asking its foreign allies for air defence systems to protect vital infrastructure since the beginning of Moscow’s invasion, but expressed frustration at the lack of supply.

“The ball is in the court of our partners,” he said.

(Reporting by Max Hunder; Editing by Chris Reese and Jonathan Oatis.)