Kyrylo Tymoshenko, the deputy head of President Volodymyr Zelensky's office, said the evacuation effort was stopped because the city of Mariupol remained under fire on Saturday.
The Russian side is not holding to the ceasefire and has continued firing on Mariupol itself and on its surrounding area," he said. "Talks with the Russian Federation are ongoing regarding setting up a ceasefire and ensuring a safe humanitarian corridor.''
The Russian Defense Ministry said earlier in a statement it had agreed on evacuation routes with Ukrainian forces for Mariupol, a strategic port in the southeast, and for the eastern city of Volnovakha.
But a city official reported that shelling continued in his area Saturday despite the deal, a sign of the fragility of efforts to stop fighting across the country.
Putin warns against no-fly zone
Meanwhile in Russia, President Vladimir Putin said Saturday he had no intention of declaring martial law, as his country's military incursion in Ukraine enters its second week.
"Martial law should only be introduced in cases where there is external aggression ... we are not experiencing that at the moment and I hope we won't," Putin said during a televised meeting with employees of Russia's flagship carrier Aeroflot.
Ther Russian President warned that any country that sought to impose a no-fly zone over Ukraine would be considered by Moscow to have entered the conflict.
"Any movement in this direction will be considered by us as participation in an armed conflict by that country," the Russian leader said during a meeting with Aeroflot employees
Russian defense officials announced a a temporary cease-fire in two Ukrainian cities to allow civilians to evacuate, but a local official reported that shelling continued in his area Saturday despite the deal, a sign of the fragility of efforts to stop fighting across the country.
The Russian Defense Ministry said in a statement it had agreed on evacuation routes with Ukrainian forces for the strategic port of Mariupol in the southeast and the eastern city of Volnovakha, which would be the first breakthrough in allowing people to escape the war . The vaguely worded statement did not make clear how long the routes would remain open.
Mariupol had become the scene of growing misery amid days of shelling 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 there said the cease-fire there was to last until 4 p.m. (2 p.m. GMT) and an evacuation was beginning at 11 a.m. (9 a.m. GMT.) Pavlo Kirilenko, head of the Donetsk military-civil administration that includes Mariupol, said the humanitarian corridor would extend from the city to Zaporizhzhia, about 226 kilometers (140 miles) away.
But Mariupol deputy mayor Serhiy Orlov later told the BBC that the Russians "continue to use hard artillery and rockets to bomb Mariupol. That's why people are very scared, but anyway they go to three specific points from which we will go to evacuate them by municipal buses.''
The head of Ukraine's security council, Oleksiy Danilov, had urged Russia to create humanitarian corridors to allow children, women and the older adults to flee the fighting, calling them "question No. 1.''
Diplomatic efforts continued as U.S. 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. Blinken would visit a border post to meet refugees later in the day.
As Russian forces batter strategic locations elsewhere, Ukrainian President Volodymyr Zelensky has lashed out at NATO for refusing 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.''
No "no-fly zone"
NATO said a no-fly zone could provoke widespread war in Europe with nuclear-armed Russia. But as the United States and other NATO members send weapons for Kyiv and more than 1 million refugees spill through the continent, the conflict is already drawing in countries far beyond Ukraine's borders.
Russia continues to crack down on independent media reporting on the war, also blocking Facebook and Twitter, and more outlets say they are pausing their work inside the country.
And in a warning of a hunger crisis yet to come, the U.N. World Food Program says millions of people inside Ukraine, a major global wheat supplier, will need food aid "immediately.''
Ukraine's president was set to brief U.S. senators Saturday by video conference as Congress considers a request for $10 billion in emergency funding for humanitarian aid and security needs.
In a bitter and emotional speech late Friday, Zelensky criticized NATO over the lack of a no-fly zone, warning that "the history of Europe will remember this forever.''
A no-fly zone would bar all unauthorized aircraft from flying over Ukraine.
NATO Secretary General Jens Stoltenberg had ruled out that possibility. "The only way to implement a no-fly zone is to send NATO fighter planes into Ukrainian airspace, and then impose that no-fly zone by shooting down Russian planes,'' he said.
In a separate video message to antiwar protesters in several European cities, Zelensky appealed for help. "If we fall, you will fall,'' he said.
The U.N. Security Council scheduled an open meeting for Monday on the worsening humanitarian situation. The United Nations estimates that 12 million people in Ukraine and 4 million fleeing to neighboring countries in the coming months will need humanitarian aid.
Zaporizhzhia Nuclear Plant Attack
ussia's attack on Friday on Ukraine's largest nuclear power plant, in Zaporizhzhia, caused global alarm, but Russian forces did not make significant progress in their offensive to sever Ukraine's access to the Black Sea and the Sea of Azov, which would deal a severe blow to the country's economy.
A vast Russian armored column threatening Ukraine's capital remained stalled outside Kyiv, but Russia's military has launched hundreds of missiles and artillery attacks on cities and other sites across the country.
As homes in the northern city of Chernihiv burned from what locals described as Russian shelling, one resident accused Europe of merely looking on. "We wanted to join NATO and the EU and this is the price we are paying, and NATO cannot protect us," she said.
At least 331 civilians have been confirmed killed since the fighting began but the true number is probably much higher, the U.N. human rights office said.
Kyiv's central train station remained crowded with people desperate to join the more than 1.4 million who have fled Ukraine. "People just want to live,'' one woman, Ksenia, said.