Russia launched a new widespread attack on Ukraine’s energy infrastructure overnight, forcing the country to implement emergency power outages, Ukrainian authorities said on Friday.

“The enemy continues its terror. Once again, the energy sector across Ukraine is under massive attack,” Ukrainian energy minister German Halushchenko said on his official Facebook page.

The extent of the damage had yet to be clarified, he said, while urging people to remain in shelters.

Streets in the capital Kyiv remained largely empty Friday morning as Ukraine’s air force warned of the threat of ballistic and cruise missiles potentially targeting parts of the country.

Ukrenergo, Ukraine’s energy grid operator, said it was introducing emergency power outages across the country.

Moscow’s forces have intensified bombardments of Ukraine in recent months, leaving the country in a precarious position as the war grinds into its third winter.

Last month, Russian President Vladimir Putin threatened to strike Ukraine again with a new nuclear-capable ballistic missile following a widespread attack on critical energy infrastructure that left more than a million households in Ukraine without power.

Russia’s latest assault comes after Moscow vowed on Thursday to respond to a Ukrainian attack on a city in southwest Russia, which Russia claimed involved six US-made ATACMS ballistic missiles.

Ukraine acknowledged making “tangible hits on Russian targets,” Wednesday, including military and energy facilities, but has not said what type of missiles were used.

The United States on Thursday announced a $500 million aid package for Ukraine in the coming days that will pull equipment out of US military stocks.

The Biden administration is working to surge deliveries of weapons to Ukraine in its final days in office in a concerted effort to put Kyiv on a strong footing going into 2025, according to a senior administration official.