Kyiv Regional Administration Head Oleksiy Kuleba said, "Russia is creating a humanitarian crisis in the Kyiv region, frustrating the evacuation of people and continuing bombardment and shelling of small communities."

Sirens sounded in the sky over the Ukrainian capital on Wednesday, and officials said they had strengthened defenses in major cities threatened by Russian forces, while authorities renewed efforts to evacuate civilians from besieged residential areas.

Ukrainian officials announced that Russia agreed to a new one-day ceasefire along several evacuation routes for people fleeing cities, including Mariupol, which has seen some of the worst cases of the war. Russian shelling there has destroyed buildings and left the area without water or heating or operating sewage networks or telephone service. Local officials said they intend to begin digging mass graves for the dead.

Thousands of people, both civilians and soldiers, are believed to have been killed in two weeks of fighting since the invasion by President Vladimir Putin’s forces. The United Nations estimates that more than two million people have fled the country. Many have become trapped inside cities that have been shelled and surrounded by Russian forces, whose advance has slowed due to stiffer-than-expected Ukrainian resistance.

Repeated alarms on Wednesday morning urged residents of the capital Kyiv to head quickly to shelters amid fears of missile shelling. Kyiv has been relatively quiet in recent days, despite Russian artillery shelling the city’s suburbs.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said, "A new effort is scheduled for Wednesday to establish safe corridors for people to flee Mariupol, Sumy in the northeast, Enerhodar in the south, Volnovakha in the southeast, Izyum in the east, and several cities in the Kyiv region."

Kyiv Regional Administration Head Oleksiy Kuleba said, "Russia is artificially creating a humanitarian crisis in the Kyiv region, frustrating the evacuation of people and continuing bombardment and shelling of small communities."

In the city’s suburbs, police officers and soldiers helped elderly residents leave their homes on Tuesday as people made their way along a destroyed bridge attempting to flee the city of Irpin, which has a population of 60,000 and has been targeted by Russian shelling.

Meanwhile, the General Staff of the Ukrainian Armed Forces said in a statement that Russian forces placed military equipment in farms and between residential buildings in the northern city of Chernihiv. It added that Russians dressed in civilian clothes are advancing south toward the city of Mykolaiv, a shipbuilding center on the Black Sea with half a million inhabitants.

The Ukrainian General Staff said the Ukrainian army is building its defenses in cities in the north, south, and east, and forces around Kyiv against the Russian offensive.

The fighting has largely thwarted previous attempts to establish corridors to safely evacuate civilians.

One evacuation appeared successful on Tuesday, with Ukrainian authorities saying 5,000 civilians, including 1,700 foreign students, were able to flee the city of Sumy, which has a population of a quarter of a million and has seen heavy shelling.

Regional Administration Head Dmytro Zhyvytsky said this corridor would be reopened for 12 hours on Wednesday, with buses having transported people southwest of the city of Poltava the previous day to let more residents leave.

Priority is given to pregnant women, women with children, the elderly, and people with disabilities.

In the south, Russian forces advanced deeply along the Ukrainian coast in an attempt to establish a land bridge to the Crimean Peninsula, which Moscow seized from Ukraine in 2014. As part of these efforts, Russian soldiers surrounded the port of Mariupol overlooking the Sea of Azov.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said Mariupol is in a "catastrophic situation."

Natalia Modrinenko, a senior member of the UN mission in Ukraine, told the Security Council that Mariupol’s residents "have been effectively taken hostage" due to the siege. Her voice trembled emotionally as she described how a six-year-old girl died shortly after her mother was killed in Russian shelling. She said, "She was alone in the last moments of her life."

With the electricity cut off, many people rely on their car radios for information, getting news from stations broadcasting from areas controlled by Russian forces or Russia-backed separatists.

Edited by: Dima Abu Khair