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

President Joe Biden spoke with Ukrainian President Volodymyr Zelenskyy on Sunday to discuss continued support for Ukraine's defense amid Russian attacks on critical infrastructure, according to a White House readout of their call.

"President Biden highlighted how the U.S. is prioritizing efforts to strengthen Ukraine's air defense through our security assistance, including the December 9 announcement of $275 million in additional ammunition and equipment that included systems to counter the Russian use of unmanned aerial vehicles," the White House said.

"President Biden also highlighted the November 29 announcement of $53 million to support energy infrastructure to strengthen the stability of Ukraine's energy grid in the wake of Russia's targeted attacks," it added.

-ABC News' Justin Ryan Gomez

A senior U.S. official met with a Russian delegation in Istanbul on Friday to discuss "a narrow set of bilateral issues," according to a spokesperson from the State Department.

Citing a hesitancy to discuss "private diplomatic discussions," the spokesperson declined to provide additional detail, but other sources say the agenda was focused on embassy staffing levels, visas, and related matters.

A spokesperson added that the war in Ukraine was not discussed, nor was Paul Whelan’s case.

The meeting was initially reported by Russian News Agency TASS.

-ABC News' Shannon Crawford

The U.S. Department of Treasury issued sanctions against four Russians accused of forcibly seizing personal data and conducting interrogations and searches against Ukrainian citizens to determine if they have any connections to the Ukrainian government or military.

There are also allegations that deportations, disappearances and torture have also been carried out.

Two of those sanctioned "oversaw the filtration of city government officials and other civilians from Mariupol, Ukraine, including through the filtration center in Manhush, Ukraine. Witnesses have reported insufficient food supplies, overcrowded cells, and beatings at the Manhush filtration center. One witness overheard Russia’s soldiers discussing shooting people who underwent filtration at Manhush," according to a press release from the Treasury.

The Treasury is also sanctioning members of Russia's Central Election Commission for overseeing the sham referenda held in Russian-controlled areas of Ukraine in September, during which Ukrainians were forced to vote for annexation.

-ABC News' Sarah Kolinovsky

A Russian airstrike that struck Kurakhov, a city in Donetsk Oblast in southeastern Ukraine, has killed 10 people, Ukrainian President Volodymyr Zelenskyy announced on Wednesday.

Civilian areas such as a market, gas station, bus station and a residential building were among the targets that were struck, Zelenskyy said.