Russia-Ukraine updates: Putin suspends key US-Russia nuclear treaty in speech denouncing West

A Ukrainian drone attack on the Engels Air Force Base in southern Russia killed three, Russia’s Ministry of Defense said.

A spokesman for Ukrainian Air Force confirmed the attack, saying, “If the Russians thought the war would not touch them they were wrong.”

Russian air defence reportedly shot down a Ukrainian drone flying at low altitude, but falling debris caused the casualties in the overnight attack.

The Engels base lies just over 300 miles northeast of Ukraine's border with Russia. The facility has been repeatedly used by Russia to carry out missile strikes on targets in Ukraine.

Ukrainian forces had attacked another Russian air base on Dec. 5, killing three and damaging two strategic bombers.

-ABC News’ Britt Clennett

The Pentagon is weighing whether to carry out Patriot missile training for Ukrainian troops inside the United States, according to two U.S. officials.

If so, it would mark the first time Ukrainian forces trained inside the U.S. since the start of Russia's invasion.

The officials say the Army base at Fort Sill, Oklahoma, is being considered as the site for stateside training.

Last week, a senior defense official told reporters that several options were being considered for training that could last several months. However, no decision has been made and it is still possible that the training may take place in Germany, as previously reported.

Weapons systems training for Ukrainian troops has taken place only in Ukraine.

- ABC News' Luis Martinez

The United States is fighting a "proxy war" on "Ukrainian territory," Russia's ambassador to the U.S., Anatoly Antonov, claimed during an interview with Russian media Friday.

"Let me remind the viewers that a proxy war means an agent’s war, a war by proxy. Actually, this is what the Americans are doing on Ukrainian territory," Antonov said.

He continued, "Today, no one hides the true goals of the White House policy towards us. On all TV channels, political commentators talk about the need to intensify the U.S. proxy war against the Russian Federation."

Antonov stated that the risk of a clash "between the two great powers [Russia and the U.S.]" is "high."

- ABC News' Will Gretsky

The United States announced Thursday it is imposing sanctions against 10 Russian entities that support the Kremlin's naval operations.

“In the wake of Russian naval operations against Ukrainian ports, including those that are providing much-needed food and grain to the world, the United States today is imposing sanctions on Russian naval entities,” U.S. Secretary of State Antony Blinken said in a statement.

The State Department said it expects the sanctions will place "severe costs on Russia’s defense establishment."

The sanctions are being imposed against Russian companies linked to both the defense and marine sectors of Russia’s economy, the State Department said.

Among the entities being sanctioned are the Rigel Battery Company, which has provided the Russian Navy with batteries for 15 years; Elektropribor, which produces navigation systems for Russian combat ships; and Avorora, which supplies automated control systems for Russian military surface ships and submarines.

"The United States remains determined to use all appropriate measures to deter Russia's attacks on Ukraine -- whether those attacks be from the air, land, or sea," Blinken said. "These accountability measures underscore a simple message: the Kremlin must end its brutal campaign against Ukraine."

The State Department and the U.S. Treasury Department also imposed sanctions against a company owned by Russian oligarch Vladimir Potanin.

A close associate of Russian President Vladimir Putin and one of the richest people in Russia, Potanin owns Interros, a company that carries out business "across nearly all sectors of Russia’s economy," the Treasury Department said in a statement.

The State Department said it has identified Potanin's super yacht "Nirvana" -- which is worth hundreds of millions of dollars -- as blocked property.

Additional sanctions were levied against five members of the state-owned Russian Railways’ board of directors and nearly 30 heads of regions and governors the State Department said “oversee and enforce the conscription of citizens in response to Russia’s recent mobilization order.”

-ABC News' Shannon Crawford