The U.S. reportedly has information indicating Russia to be preparing a “false-flag operation in eastern Ukraine” in an attempt at creating pretext for and justifying an invasion of the former Soviet republican, CNN reports, per a U.S. official.

The official also said the U.S. has evidence that Russia has prepositioned operatives “trained in urban warfare and in using explosives to carry out acts of sabotage against Russia’s own proxy forces,” writes CNN. A false-flag attack is one designed to look as though it were carried out someone other than the person (or, in this case, country) responsible.

Notably, Ukranian government servers were also hit by a “massive” overnight cyberattack on Friday, which, among other things, replaced the homepage for the Foreign Ministry website with a temporary message warning Ukranians to “be afraid and expect the worst,” writes CBS News.

Though a claim of responsibility for the attack has yet to be made, Ukraine’s ambassador in Washington, D.C. had just hours before told CBS News her country “believed a cyberattack would precede any major military action by [Russian President] Vladimir Putin’s forces,” CBS News reports. Ukraine has also blamed parties with links to the Russian government for previous cyber assaults.

The U.S. official speaking with CNN said the White House thinks Russia could be prepping for a Ukraine invasion “that may result in widespread human rights violations and war crimes should diplomacy fail to meet their objectives.”

“The Russian military plans to begin these activities several weeks before a military invasion, which could begin between mid-January and mid-February,” the official said. “We saw this playbook in 2014 with Crimea.”

The official also noted how Russian influence actors have already begun preparing Russian audiences for an attack, a strategy involving emphasizing narratives of anti-Ukranian propaganda.