LVIV, Ukraine (NewsNation) — Talks between Russia and Ukraine are set to resume Monday, Kremlin spokesperson Dmitry Peskov was quoted as saying Sunday by the RIA news agency.

Peskov made the comments after Ukrainian presidential adviser Oleksiy Arestovych said Ukraine and Russia were actively conducting talks Sunday, with the situation around the besieged city of Mariupol a particular focus.

Arestovych said Ukraine had enough troops deployed in the battered and encircled port city of Mariupol to prevent its capture by Russian forces.

Ukraine’s military said Russian forces captured Mariupol’s eastern outskirts, tightening their siege of the strategic port. Taking Mariupol and other ports on the Azov Sea could allow Russia to establish a land corridor to Crimea, which it seized from Ukraine in 2014.

Russian troops also pillaged a humanitarian convoy that was trying to reach Mariupol, where more than 1,500 people have died, a Ukrainian official said.

Since Russia’s invasion more than two weeks ago, at least 596 civilians have been killed, according to the U.N., though it believes the true toll is much higher. Millions more have fled their homes amid the largest land conflict in Europe since World War II.

Also Sunday, more than 30 Russian missiles hit a military training base near Yavoriv on Sunday, less than 15 miles from the Polish border, killing 35 people and wounding more than 130. The strike followed Russian threats that foreign weapon shipments to Ukrainian fighters will be considered legitimate targets for attack.

The facility, also known as the International Peacekeeping and Security Center, has long been used to train Ukrainian military personnel, often with instructors from the United States and other NATO countries.

NATO said Sunday that it currently does not have any personnel in Ukraine. A NATO official didn’t respond to questions about when the alliance last had personnel at the training base.

The attack raises concerns about the safety of people in Lviv, the largest Ukrainian city near Poland’s border. It has so far been spared the scale of destruction unfolding further east and has served as a temporary destination for many of the nearly 2.6 million refugees who have fled the country.

“Citizens are afraid,” said a local mayor, “and I believe they will flee out of the country,” like the millions of refugees already crowding into countries further west.

White House national security adviser Jake Sullivan said the West would respond if Russia’s armaments travel outside Ukraine and hit any NATO members, even accidentally.

Lviv governor Maksym Kozytskyi said most of the missiles fired Sunday “were shot down because the air defense system worked.”

Continued fighting on multiple fronts heaped further misery on the country Sunday and provoked renewed international outrage.

Russian fighters also fired at the airport in the western city of Ivano-Frankivsk, which is less than 94 miles north of Romania and 155 miles from Hungary, countries that also are NATO allies. The airport, which includes a military airfield as well as a runway for civilian flights, also was targeted Friday.

Ukrainian authorities said Russian airstrikes on a monastery and a children’s resort in the eastern Donetsk region hit spots where monks and refugees were sheltering, wounding 32 people.

Another airstrike hit a westward-bound train evacuating people from the east, killing one person and injuring another, Donetsk’s chief regional administrator said.

To the north, in the city of Chernihiv, one person was killed and another injured in a Russian airstrike that destroyed a residential block, emergency services said.

Around the capital, Kyiv, a major political and strategic target for the invasion, fighting also intensified, with overnight shelling in the northwestern suburbs and a missile strike Sunday that destroyed a warehouse to the east.

A U.S. journalist being treated at a hospital says that he and a U.S. colleague were shot after they were stopped at a checkpoint just after a bridge in Irpin, a town near Kyiv.

Juan Arredondo told Italian journalist Annalisa Camilli in an interview from the hospital before being taken for surgery that the colleague who was with him was hit in the neck and remained on the ground earlier on Sunday.

Camilli told The Associated Press that she was at the hospital when Arredondo arrived and that Arredondo had himself had been wounded, hit in the lower back when stopped at a Russian checkpoint.

Arredondo told Camilli he didn’t have further information on the fellow U.S. journalist, whom he identified as Brent Renaud, a friend. He told Camilli they were filming refugees fleeing the area when they were shot at while in a car approaching a checkpoint. The driver turned around but the firing at them continued, Arredondo added.

A statement from Kyiv regional police said that Russian troops opened fire on the car, and that one journalist died. Arredondo said that an ambulance brought him to the hospital and that Renaud was “left behind.”

In Irpin, a suburb about 12 miles northwest of central Kyiv, bodies laid out in the open Saturday on streets. Chief regional administrator Oleksiy Kuleba said Russian agents were in the capital and its suburbs, marking out possible future targets.

Ukrainian and European leaders have pushed with limited success for Russia to grant safe passage to civilians trapped by fighting, though Ukrainian President Volodymyr Zelenskyy said authorities have managed to evacuate nearly 125,000 people from combat zones.

Ukrainian authorities said more than 10 humanitarian corridors would open Sunday, with agreement from Russia, including Mariupol.

The war has repeatedly raised the specter of nuclear accidents, as fighting occurred around nuclear power plants. On Sunday, Ukraine said it restored a broken power line to the decommissioned Chernobyl plant, scene of the world’s worst nuclear disaster in 1986.

The plant was knocked off the grid last week and relying on generators. That raised concerns about its ability to keep spent fuel cool, though the International Atomic Energy Agency played down those worries.

In some of his strongest denunciations yet of the war in Ukraine, Pope Francis on Sunday decried the “barbarianism” of the killing of children and other civilians and pleaded for the attacks to end “before cities are reduced to cemeteries.”

Francis said Mariupol, which “bears the name” of the Virgin Mary, has “become a city martyred by the heartbreaking war that is devastating Ukraine.”