Ukraine warned its citizens to “expect the worst” after the country was hit by a massive cyberattack Friday. The Ukrainian Foreign Ministry said it’s too soon to tell who was behind the attack but added, “There is a long record of Russian cyber assaults against Ukraine in the past.”

According to Ukraine’s Security Service, the cyberattack hit government bodies including the Ministry of Foreign Affairs, the Cabinet of Ministers, and the Security and Defense Council.

The cyberattack follows the last of three meetings regarding Russia’s security demands for the U.S. and NATO. One of the demands is for NATO to not expand eastward or allow Ukraine to become a member.

“Russia raised its concerns,” White House National Security Adviser Jake Sullivan said. “We raised our concerns, including the actions Russia has taken to undermine European security that Secretary Blinken spoke so eloquently about last week.”

On Friday, Russia’s Foreign Minister warned Russia won’t wait on a response and wants an answer in writing from the U.S. and NATO by next week.

Meanwhile, Russia has amassed more than 100,000 troops on its border with Ukraine and released pictures on television of its troops running drills.

The Biden administration has determined a Russian effort is underway to create a pretext for its troops to potentially further invade Ukraine. Moscow has already prepositioned operatives to conduct “a false-flag operation” in eastern Ukraine, a U.S. official said Friday.

The administration believes Russia is also laying the groundwork through a social media disinformation campaign by framing Ukraine as an aggressor that has been preparing an imminent attack against Russian forces in eastern Ukraine, according to an anonymous official.

The anonymous official also said U.S. intelligence officials have determined Russia has already dispatched operatives trained in urban warfare who could use explosives to carry out acts of sabotage against Russia’s own proxy forces — blaming the acts on Ukraine — if Russian President Vladimir Putin decides he wants to move forward with an invasion.