The US State Department issued a security alert on Monday warning that Russia is stepping up efforts to launch strikes against civilian infrastructure and government facilities in Ukraine in the coming days.

The US Embassy in Kyiv has urged US citizens still in Ukraine to leave the country immediately. “If you hear a loud explosion or sirens are activated, seek shelter immediately,” the State Department said in its alert.

“If you’re in a house or building, go to the lowest level of the structure with the fewest exterior walls, windows, and openings; close all doors and sit near an interior wall, away from any windows or openings.

The State Department issued the alert after the US intelligence community on Monday declassified a finding that determined Russia would increasingly target Ukrainian civilian infrastructure, according to a US official familiar with intelligence.

The official was not authorized to comment publicly on the discovery and spoke on condition of anonymity.

The new information comes as Russia’s brutal invasion of Ukraine will reach the six-month mark on Wednesday, which coincides with the day of Ukraine’s independence from Soviet Union rule.

President Joe Biden spoke to British Prime Minister Boris Johnson, French President Emmanuel Macron and German Chancellor Olaf Scholz on Sunday about concerns over bombings near the Zaporizhzhia nuclear power plant in southeastern Ukraine and called on the United Nations nuclear watchdog to visit the plant. The official, however, said the discovery of the intelligence was not specifically related to concerns about Zaporizhzhia.

The Biden administration is fighting to get Western allies — and Washington — to focus on keeping pressure on Russian President Vladimir Putin. Senate Republican Leader Mitch McConnell said Monday that “the most important thing happening in the world right now is beating the Russians in Ukraine.”

Speaking at a luncheon in Scott County, Kentucky, McConnell said his only fear was that the United States and others would “lose interest” as the war drags on. “We have to stick with them,” McConnell said.

“It’s important to us, and to the rest of the world, that they succeed.” — PA Congressional Correspondent Lisa Mascaro contributed reporting.