LVIV, Ukraine (AP) — President Putin said Saturday that Moscow would consider any third-party declaration of a no-fly zone over Ukraine as “participation in the armed conflict.”

Speaking at a meeting with female pilots on Saturday, Mr. Putin said Russia would view “any move in this direction” as an intervention that “will pose a threat to our service members.”

“That very second, we will view them as participants of the military conflict, and it would not matter what members they are,” the Russian president said.

President Zelensky has pushed NATO to impose a no-fly zone over his country, warning that “all the people who die from this day forward will also die because of you” as Russian forces were battering strategic locations in Ukraine.

NATO has said a no-fly zone, which would bar all unauthorized aircraft from flying over Ukraine, could provoke widespread war in Europe with nuclear-armed Russia.

Earlier, a limited cease-fire that Russia declared to allow civilians to evacuate two cities in Ukraine quickly fell apart Saturday, and Ukrainian officials blamed Russian shelling for blocking the promised safe passage as Moscow tightened its grip on the southern coast and residents raced to escape areas not under siege.

The Russian defense ministry said it had agreed on evacuation routes with Ukrainian forces for Mariupol, a strategic port in the southeast, and the eastern city of Volnovakha. The two cities have been under attack for days, producing scenes of desperation, destruction, and death that mirrored those elsewhere from the war in Ukraine.

The struggle to enforce the cease-fire showed the fragility of efforts to stop fighting across Ukraine as the number of people fleeing the country reached 1.4 million on the 10th day after Russian forces invaded its neighbor.

“We are doing everything on our part to make the agreement work,” Mr. Zelensky said. “This is one of the main tasks for today. Let’s see if we can go further in the negotiation process.”

“The Russian side is not holding to the cease-fire and has continued firing on Mariupol itself and on its surrounding area,” the deputy head of Mr. Zelensky’s office, Kyrylo Tymoshenko, said. “Talks with the Russian Federation are ongoing regarding setting up a cease-fire and ensuring a safe humanitarian corridor.”

Russia breached the deal in Volnovakha as well, Deputy Prime Minister Iryna Vereshchuk told reporters. “We appeal to the Russian side to stop firing,” she said. Meanwhile, Moscow outlet RIA Novosti carried a Russian defense ministry claim that the firing came from inside both cities against Russian positions.

Mariupol had been the scene of growing misery in recent days amid an assault that knocked out power and most phone service and raised the prospect of food and water shortages for hundreds of thousands of people in freezing weather. Pharmacies are out of medicine, Doctors Without Borders said.

A top official in Mariupol, Pavlo Kirilenko, the head of the Donetsk military-civil administration that includes the city, had said the humanitarian corridor would extend to Zaporizhzhia, 140 miles away.

In comments carried on Ukrainian television, Mariupol’s mayor, Vadym Boychenko, said thousands of people had gathered for safe passage out of the city and buses were departing when shelling began.

“We value the life of every inhabitant of Mariupol and we cannot risk it, so we stopped the evacuation,” he said.

Before Russia announced the limited cease-fire, Ukraine had urged Moscow to create humanitarian corridors to allow children, women, and older adults to flee the fighting, calling them “question no. 1.”

The Russian foreign minister, Sergey Lavrov, on Saturday asserted that “the Ukrainian side, the most interested side here, it would seem, is constantly making up various pretexts to delay the beginning of another meeting.” He said Russia was ready for a third round of talks.

Diplomatic efforts continued as the American secretary of state, Antony Blinken, arrived in Poland to meet with the prime minister and foreign minister, a day after attending a NATO meeting in Brussels in which the alliance pledged to step up support for eastern flank members.

Aeroflot, Russia’s flagship state-owned airline, announced that it plans to halt all international flights, except to Belarus, starting Tuesday in the wake of Western sanctions imposed on Russia.

While a vast Russian armored column threatening Ukraine’s capital remained stalled outside Kyiv, the new shelling in Mariupol showed Russia’s determination to cut Ukraine off from access to the Black Sea and the Sea of Azov, further damaging the country’s economy.

Despite the shelling, a presidential adviser, Oleksiy Arestovich, said the situation was generally quiet Saturday and Russian forces “have not taken active actions since the morning.”

— YURAS KARMANAU, Associated Press