An American journalist has been killed in Ukraine, The New York Times confirmed Sunday.

Brent Renaud, a photographer and filmmaker, had worked as a contributor for the newspaper but was not on assignment for The Times when he was killed, according to a statement from the news outlet.

"We are saddened to hear of Brent Renaud's death. Brent was a talented filmmaker who had contributed to The New York Times over the years," the newspaper said in its statement posted on Twitter. "Though he had contributed to The Times in the past (most recently in 2015), he was not on assignment for any desk at The Times in Ukraine. Early reports that he worked for (The) Times circulated because he was wearing a Times press badge that had been issued for an assignment many years ago."

Kyiv's police chief later confirmed Renaud's death in a Facebook post.

A State Department spokesperson also confirmed Renaud's death.

"We offer our sincerest condolences to his family on their loss and offering all possible consular assistance," the State Department spokesperson said.

Time magazine editor in chief and CEO Edward Felsenthal said Renaud had been working in recent weeks on a Time Studios project focused on the global refugee crisis.

"We are devastated by the loss of Brent Renaud. As an award-winning filmmaker and journalist, Brent tackled the toughest stories around the world often alongside his brother Craig Renaud," Felsenthal said in a joint statement with Ian Orefice, president and COO of Time and Time Studios.

White House national security adviser Jake Sullivan told CBS News that he had just learned of Renaud's death Sunday morning and described it as "obviously shocking and horrifying."

"I will be consulting with my colleagues. We’ll be consulting with the Ukrainians to determine how this happened and then to measure and execute appropriate consequences as a result of it," Sullivan said. "I will just say that this is part and parcel of what has been a brazen aggression on the part of the Russians where they have targeted civilians, they have targeted hospitals, they have targeted places of worship and they have targeted journalists."

British Prime Minister Boris Johnson called Ukraine President Volodymyr Zelenskyy on Sunday and both leaders condemned the killing of Renaud, according to a read out of the call released by Johnson's office.

-ABC News' Matt Foster

One of Russia’s negotiators in cease-fire talks with Ukraine said he believes "substantial progress" has been made and that the two sides might reach a "unified position" in the near future, the Russian state news agency TASS reported Sunday.

Leonid Slutsky, a senior Russian lawmaker who has taken part in the talks, was quoted by TASS as saying, “The progress in the talks between Russia and Ukraine in the near future can grow into a unified position of both delegations."

The two sides have held three rounds of face-to-face talks in Belarus and have been talking by video conference in recent days.

Russia has suggested its conditions for ending the war would require Ukraine to change its constitution to guarantee it will never join a political bloc, specifically NATO or the European Union, as well as recognizing Crimea as part of Russia and the two Russian-controlled separatist areas in the Donbas region of in eastern Ukraine as independent.

Ukraine previously said Russia continues to demand its surrender.

Ukraine's lead negotiator and presidential adviser Mykhailo Podolyak also issued a hopeful statement Sunday, saying the two sides are moving toward compromises and that they are now discussing concrete points. Podolyak told the independent Russian newspaper Kommersant that Russia is looking at the situation “far more properly."

"They have started to talk about something and not just throw out ultimatums," Podolyak told the newspaper. But he said more time was needed for Russia to fully understand the reality of its situation and the need to further compromise on its demands.

According to Kommersant, Podolyak said working groups are developing the legal aspects of documents the two sides might eventually be able to sign. For now, both have agreed to keep the proposals confidential until they have an agreement, he said.

He said the negotiations have focused on conditions for a cease-fire and peace agreement, how to compensate Ukraine for the damage to its infrastructure and the process of withdrawing Russian troops. Notably, he said the key point of a peace agreement is the issue of "security guarantees" for both Russia and Ukraine.

“We have all the proposals, which one way or the other protect these interests, get Ukraine out from under attack from the point of view that similar situation won’t be repeated, get Ukraine to some kind of compensatory things in the right sense. And I emphasize again -- the Russian side already looks at [the situation] far more properly. But some time must pass still so they understood 100% the situation in which very much Russia, not Ukraine, has fallen," Podolyak said.

Podolyak said he hopes a fourth round of talks will be held in person.

A Russian airstrike killed 35 people early Sunday morning at a military facility in western Ukraine, miles from the Polish border.

The Lviv Regional Military Administration said at least eight Russian rockets struck a training facility near Yavoriv, a town about 35 miles west of Lviv and 10 miles from the Polish border. The attack could be heard from Lviv.

Thirty-five people were killed and 134 were wounded, according to Maksym Kozytskyi, head of the regional military administration. It was unclear whether civilians were among the injured.

"Today the Lviv region was hit by missiles, preliminary by jets, stationed in Saratov, Russia, not flying into Ukrainian territory," Kozytskyi said. "Preliminary more than 30 missiles were launched. Anti-missile defense worked, some amount of missiles were shot down. The Yavoriv firing ground came under attack."

Yavoriv sits along one of the main routes used to bring supplies into Ukraine from Poland, a pathway also used in recent weeks by refugees fleeing the Russian invasion.

The facility struck on Sunday is near the International Center for Peacekeeping and Security, known as the base where for years NATO military instructors, including Americans, trained Ukrainian troops to fight against Russia in the east.

The administration said earlier on Sunday that nine people were killed and 57 were wounded.

The mayor of Ivano Frankivsk, a southwestern city, also confirmed a strike on the city’s airport early on Sunday. It’s the third such strike, official said.

-ABC News’ Kirit Radia, Julia Drozd, Patrick Reevell and Clark Bentson

Ukrainian Deputy Prime Minister Iryna Vereshchuk posted an update Saturday on the country's evacuation progress.

About 13,000 Ukrainians were evacuated Saturday, which was half the number from Friday, she said.

Nine out of 14 humanitarian corridors were open Saturday, according to Vereshchuk.

About 8,000 refugees left Sumy, more than 3,000 left Konotop, 800 people were taken out of Gostomel and about a thousand people evacuated Nemeshaevo, Vereshchuk said.

About a thousand people were rescued from Bucha, including patients at a nursing home, she said.

However, Russia didn't let a convoy through the checkpoint in Vasilyevka and as a result no one could evacuate from the Zaporіzhya region, Vereshchuk said.

A Ukrainian convoy also did not reach Mariupol, because it got stuck at a Russian checkpoint, according to Vereshchuk. The convoy will try to take people out from the locations Sunday, she said.

-ABC News' Jason Volack