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

In his Sunday Mass at the Vatican, Pope Francis directed his sermon at Russian President Vladimir Putin, saying, "stop this spiral of violence and death" in Ukraine.

Speaking to worshipers in St. Peter's Square, the pontiff denounced Putin's veiled threats of nuclear war as "absurd," according to The Associated Press.

In a message to Ukrainian President Volodymyr Zelenskyy, Francis asked him to "be open" to serious peace talks.

The pope implored the international community to "use all diplomatic instruments" to end the war, describing the seven months of fighting as a "huge tragedy" and "horror."

"How the war is going in Ukraine has become so grave, devastating and threatening that it sparks great worry," Francis said. "In fact, this terrible, inconceivable wound of humanity, instead of shrinking, continues to bleed even more, threatening to spread."

In apparent reference to Putin's annexation of four Russian-controlled regions of eastern and southern Ukraine, the pope said the actions are "contrary to the principles of international law."

"It, in fact, increases the risk of a nuclear escalation, to the point of fearing uncontrollable and catastrophic consequences on the world level," he said.

Russian forces have withdrawn their troops from the once-occupied Ukrainian city of Lyman as Ukraine's eastern counteroffensive recaptures more territory, Russia's Tass and RIA news agencies said Saturday citing the Russian defense ministry.

Lyman is 100 miles southeast of Kharkiv, Ukraine's second-largest city. Ukrainian forces had pushed across the Oskil River as part of a successful counteroffensive that allowed it to reclaim occupied territories beginning in September.

Lyman, a key transportation hub, had been an important site in the Russian front line for ground communications and logistics. Now that Ukraine has reclaimed the territory, it can push further, potentially into the occupied Luhansk region, one of the four areas Russia annexed Friday.

In a statement, the Russian Defense Ministry said it withdrew its forces due to the risk of being encircled after the Ukrainians sent reserve forces and continued the offensive.

-ABC News' Somayeh Malekian

Russian forces are accused of shelling a convoy of seven civilian cars killing 22 people, including 10 children, according to preliminary data, Olexandr Filchakov, chief prosecutor of the Kharkiv region, told ABC News.

According to preliminary data, the cars were shot by the Russian military on Sept. 25, when civilians were trying to evacuate from Kupyansk, a settlement in the Kupyansk area, Filchakov said.

The column of shot cars was discovered on Friday. Two cars burned completely with children and parents inside, Filchakov said.

Filchakov said the bodies burned completely.

Russian forces fired at the column with a 12.5 mm caliber gun. Those who remained alive were then shot at with rifles, according to Filchakov.

-ABC News' Somayeh Malekian

The White House reiterated its warning Friday that there is a risk Russia may consider the use of nuclear weapons, but there are no indications of an "imminent use of nuclear weapons."

"I've been clear myself, President Biden has been clear, the administration has been clear that there is a risk given all of the loose talk and the nuclear saber rattling by Putin, that he would consider this and we've been equally clear about what the consequences would be," National Security Advisor Jake Sullivan said.

Asked if the threat was higher now than it was at the start of the invasion of Ukraine, Sullivan wouldn't characterize a risk level, but noted that "the risk has been there from the start."

Sullivan added, "What's interesting is that at various points over the course of this conflict, including right at the outset, Putin has brandished the nuclear card. He's doing it again."

Asked by ABC's Terry Moran about Vladimir Putin's speech Friday, accusing the U.S. and the West of values equal to "Satanism" and attacking "liberal values," Sullivan said, "its raving."

-ABC News' Terry Moran and Justin R. Gomez