Ukraine Says Russia Is Shelling Promised Humanitarian Evacuation CorridorsUkraine says Russian forces are shelling agreed-upon evacuation routes from Mariupol, as well as the city itself, breaking a cease-fire that was to have gone into effect Saturday at 7 a.m. UTC, as the southern coastal city continued to endure days of relentless aerial attacks. “We are simply being destroyed,” Mayor Vadym Boichenko said of his city of nearly 450,000 people on his Telegram channel. Russian Defense Ministry spokesman Igor Konashenkov said in a broadcast video that, "Today, March the fifth, from 10:00 a.m. Moscow time (0700 GMT), the Russian side declares a cease-fire and the opening of humanitarian corridors to allow civilians to leave Mariupol and Volnovakha. Humanitarian corridors and exit routes have been agreed upon with the Ukrainian side." Mariupol officials said they are delaying the evacuation plans that called for routes to be open to vehicular traffic for five hours, and they urged residents to take shelter. Volnovakha, a southern city of about 21,000, also was targeted with Russian “heavy artillery” attacks during the temporary cease-fire, Ukrainian Deputy Prime Minister Iryna Vereshchuk said Saturday in a broadcast video. Russia’s defense ministry, however, accused Ukrainian “nationalists” of preventing civilians from fleeing Mariupol, according to RIA, Russia’s state-owned news agency. They cited no evidence to substantiate these claims. U.S. Secretary of State Antony Blinken met Saturday with Polish Foreign Minister Zbigniew Rau in Rzeszow, one day after declaring Russian forces "are increasingly using brutal methods in Ukraine, including going at civilian populations." His comments followed a Russian attack on a Ukrainian nuclear plant — the largest facility of its kind in Europe — that had sparked a fire in a building at the plant compound, which was said Friday to be extinguished. After the meeting with his Polish counterpart, Blinken reiterated at a news conference that the U.S. “will defend every inch of NATO territory" and announced the Biden administration is preparing to allocate an additional $2.75 billion in humanitarian aid for Ukrainian refugees. Blinken also praised Poland for assisting hundreds of thousands of Ukrainians who have fled their home country, saying “The people of Poland know how important it is to defend freedom.” He added, “Poland is doing vital work in response to this crisis.” Polish Foreign Minister Rau said he and Blinken discussed Polish-American bilateral relations, allied cooperation with NATO and the coordination of political activities in the Organization for Security and Co-operation in Europe. “Poland will never recognize territorial changes brought about by unprovoked, unlawful aggression," he declared. Speaking to reporters Friday before a meeting with his European Union counterparts in Brussels, Blinken said, "We are faced together with what is [Russian] President [Vladimir] Putin's war of choice: unprovoked, unjustified, and a war that is having horrific, horrific consequences." "We're committed to doing everything we can to make it stop," he added, but he ruled out imposing a no-fly zone over Ukraine, saying such an action could lead to a broader conflict. "We have a responsibility to ensure the war does not spill over beyond Ukraine. … A no-fly zone could lead to a full-fledged war in Europe," he said. The meeting in Brussels came after Ukraine accused Russia of "nuclear terror" for shelling and starting a fire at the Zaporizhzhia nuclear plant before taking control of it. The plant is in the city of Enerhodar in the country's southeast. Ukraine's nuclear inspectorate said that no radiation had leaked at the plant and that personnel were continuing to operate the facility safely. Firefighters were able to get the blaze under control, Ukrainian officials said. The United Nations Security Council held an emergency meeting Friday to discuss the attack at the request of Britain, France, Ireland, Norway and Albania. "The world narrowly averted a nuclear catastrophe last night," U.S. Ambassador to the U.N. Linda Thomas-Greenfield said during the meeting. "We've just witnessed a dangerous new escalation that represents a dire threat to all of Europe and the world." Konashenkov blamed the attack on a Ukrainian "sabotage group" that he said had occupied the plant's training building, attacked a Russian patrol and set the building on fire as it left. He offered no evidence, and no other country appeared to take the claim seriously. On the ground Despite its heavy shelling of Mariupol and Volnovakha, there were fewer Russian aerial and artillery attacks in Ukraine over the past 24 hours compared to previous days, the British defense ministry tweeted Saturday on the 10th day of Russia’s attack on its western neighbor. The ministry said Ukraine continued to control the northern cities of Kharkiv and Chernihiv, as well as Mariupol in the southeast. The ministry cited reports of street fighting in the northeastern city of Sumy and said “It is highly likely that all four cities are encircled by Russian forces” as they advance toward the southwestern city of Odessa. On Friday, Pentagon press secretary John Kirby said that Russian ground forces are attacking a Ukrainian town near Odesa and the U.S. is watching to see what it means for the city. A Russia convoy outside the capital, Kyiv, was still trying to reach the city, he said, but the "actions by the Ukrainians have in fact stalled that convoy … stopped it in some places." Ukraine's use of its air and missile defenses has been "quite extraordinary," Kirby said. A Russian diplomat said Friday that Russia has no intention of occupying Ukraine should its invasion be successful, and that its troops will withdraw once it has fulfilled its objective. Speaking to reporters at U.N. headquarters in Geneva, Russian Ambassador Gennady Gatilov called the invasion a "military operation with limited objectives," which he said were to "denazify the regime and demilitarize Ukraine." Ukraine is a country with a democratically elected Jewish president who lost relatives in the Holocaust. Many historians and political observers view Russia's invocation of World War II as disinformation. Possibility of more sanctions Blinken said Friday the United States was considering additional sanctions against Russia and had not ruled out anything. "Nothing is off the table. We are evaluating the sanctions every day," he said. The number of Ukrainians seeking refuge in other countries could reach 1.5 million by the end of the weekend, the head of the United Nations refugee agency said Saturday, an increase from the 1.3 million who already have fled. U.N. Crisis Coordinator for Ukraine, Amin Awad, who is meeting in Ukraine with local and international officials, said in a statement Saturday that efforts are underway “to urgently find operational modalities to scrape up operations across lines and from outside into areas impacted by the conflict.” VOA State Department Bureau chief Nike Ching, national security correspondent Jeff Seldin, Pentagon correspondent Carla Babb, Istanbul foreign correspondent Heather Murdock, White House correspondent Anita Powell, and senior diplomatic correspondent Cindy Saine contributed to this report. Some information came from the Associate Press, Agence France-Presse and Reuters.