A long-awaited effort to evacuate civilians from a steel plant in the Ukrainian city of Mariupol was underway Sunday, the United Nations said, while U.S. House Speaker Nancy Pelosi revealed she visited Ukraine’s president to show unflinching American support for the country’s defense against Russian aggression.

U.N. humanitarian spokesman Saviano Abreu told The Associated Press that the operation to bring civilians out of the sprawling Azovstal steel plant was being carried out with the International Committee of the Red Cross and in coordination with Ukrainian and Russian officials.

As many as 100,000 people are believed to still be in blockaded Mariupol, including up to 1,000 civilians who were hunkered down with an estimated 2,000 Ukrainian fighters beneath the Soviet-era steel plant — the only part of the city not occupied by the Russians.

The fate of the Ukrainian fighters was not immediately clear.

Like other evacuations, the success of the mission in Mariupol depended on Russia and its forces, deployed along with a long series of checkpoints before reaching the Ukrainian ones.

Zaporizhzhia, a city about 140 miles northwest of Mariupol, was the destination of the evacuation effort, Abreu said. He said women, children, and the elderly — who have been stranded for nearly two months — will be evacuated to the city, where they will receive immediate humanitarian support, including psychological services.

Mariupol has seen some of the worst sufferings of the war. A maternity hospital was hit by a lethal Russian airstrike in the opening weeks of the war, and about 300 people were reported killed in the bombing of a theater where civilians were taking shelter.

Abreu said U.N. officials would not provide additional details of the evacuation “to guarantee the safety of the civilians and humanitarians in the convoy.”

However, the Mariupol City Council said in a post on the Telegram messaging app Sunday that evacuation of civilians from other parts of the city would begin Monday morning, because of security concerns. People fleeing Russian-occupied areas in the past have described their vehicles being fired on, and Ukrainian officials have repeatedly accused Russian forces of shelling evacuation routes on which the two sides had agreed.

Ukrainian President Volodymyr Zelenskyy said in a tweet earlier Sunday that the first group of about 100 people was headed to Ukrainian-controlled territory.

“Tomorrow we’ll meet them in Zaporizhzhia. Grateful to our team! Now they, together with #UN, are working on the evacuation of other civilians from the plant,” he tweeted.

A team from Doctors Without Borders was at a reception center for displaced people in Zaporizhzhia on Sunday, in preparation for the U.N. convoy’s arrival, if successful. Stress, exhaustion, and low supplies of food were likely to have weakened the health of civilians who have been trapped underground at the plant.

Ukrainian regiment Deputy Commander Sviatoslav Palamar, meanwhile, called for the evacuation of wounded Ukrainian fighters as well as civilians. “We don’t know why they are not taken away and their evacuation to the territory controlled by Ukraine is not being discussed,” he said in a video posted Saturday on the regiment’s Telegram channel.

Video and images from inside the steel plant, shared with the AP by two Ukrainian women who said their husbands were among the fighters refusing to surrender there, showed men with stained bandages, open wounds, or amputated limbs, including some that appeared gangrenous. The AP could not independently verify the location and date of the video, which the women said was taken last week.

In Zaporizhzhia on Sunday, residents ignored air raid sirens and warnings to shelter at home to visit cemeteries, when Ukrainians observe the Orthodox Christian day of the dead.

“If our dead could rise and see this, they would say, ‘It’s not possible, they’re worse than the Germans,’” Hennadiy Bondarenko, 61, said while marking the day with his family at a picnic table among the graves. “All our dead would join the fighting, including the Cossacks.”

Russian forces have embarked on a major military operation to seize significant parts of southern and eastern Ukraine following their failure to capture the capital, Kyiv. Mariupol, a port city on the Sea of Azov, is a key target because of its strategic location near the Crimea Peninsula, which Russia seized from Ukraine in 2014.

Russia’s high-stakes offensive has Ukrainian forces fighting village-by-village and more civilians fleeing airstrikes and artillery shelling.

Ukrainian intelligence officials accused Russian forces of seizing medical facilities to treat wounded Russian soldiers in several occupied cities and towns, as well as “destroying medical infrastructure, taking away equipment, and leaving the population without medical care.”

In a Facebook post-Sunday, the Main Intelligence Directorate of Ukraine’s Ministry of Defense said that in the Volchansk, Kharkiv region, tuberculosis patients were “denied medical care and kicked out into the street” as facilities were being used to treat wounded Russian troops. It said that four hospitals in Ukraine’s east were similarly “forced to service the needs of the Russian Federation,” claiming that Russian forces organized an impromptu ammunition depot at one facility near Zaporizhzhia, and prohibited staff from providing medical care to local residents. The AP could not immediately verify the accuracy of the claims.

Getting a full picture of the unfolding battle in eastern Ukraine has been difficult because airstrikes and artillery barrages have made it extremely dangerous for reporters to move around. Also, both Ukraine and Moscow-backed rebels have introduced tight restrictions on reporting from the combat zone.

But Western military analysts have suggested the offensive in the Donbas region, which includes Mariupol, was going much slower than planned. So far, Russian troops and the separatists appeared to have made only minor gains in the month since Moscow said it would focus its military strength in the east.

Hundreds of millions of dollars in military assistance have flowed into Ukraine since the war began, but Russia’s vast armories mean Ukraine will continue to require huge amounts of support.

In the days before the war began, Western intelligence estimated Russia had positioned near the border as many as 190,000 troops; Ukraine’s standing military totals about 200,000, spread throughout the country.

 

With plenty of firepowers still in reserve, Russia’s offensive still could intensify and overrun the Ukrainians. Overall the Russian army has an estimated 900,000 active-duty personnel. Russia also has a much larger air force and navy.