ZAPORIZHZHIA, Ukraine (AP) — A first group of civilians trapped for weeks inside a steel plant in Mariupol under Russian siege was expected to reach a Ukrainian-controlled city on Monday, as a new attempt was launched to allow people sheltering elsewhere in the city to leave.

Video posted online Sunday by Ukrainian forces showed elderly women and mothers with small children climbing over a steep pile of rubble from the sprawling Azovstal steel plant and eventually boarding a bus.

The evacuation, if successful, would represent rare progress in easing the human cost of the almost 10-week war, which has caused particular suffering in Mariupol. Previous attempts to open safe corridors out of the port city on the Sea of Azov and other places have broken down. People fleeing Russian-occupied areas in the past have said their vehicles were fired on, and Ukrainian officials have repeatedly accused Russian forces of shelling agreed-upon evacuation routes.

At least some of the people evacuated from the plant were apparently taken to a village controlled by Moscow-backed separatists, though Russian state media reported they would be allowed to continue on to Ukrainian-held territory if they wanted to. In the past, Ukrainian officials have accused Moscow’s troops of forcibly relocating civilians from areas they have captured to Russia; Moscow has said the people wanted to go to Russia.

More than 100 civilians were expected to arrive in Zaporizhzhia on Monday, Ukrainian President Volodymyr Zelenskyy said Sunday.

“Today, for the first time in all the days of the war, this vitally needed green corridor has started working,” Zelenskyy said in a pre-recorded address published on his Telegram messaging channel.

While official evacuations have often faltered, many people have managed to flee Mariupol under their own steam. Anastasiia Dembytska took advantage of the brief cease-fire around the evacuation of civilians from the steel plant to leave with her daughter, nephew and dog.

She told The Associated Press she could see the steel plant from her window, when she dared to look out.

“We could see the rockets flying” and clouds of smoke over the plant, she said.

She said she had to navigate many checkpoints on the journey to Zaporizhzhia and waited 18 hours near the city before being allowed to pass.

Like many Mariupol residents, Dembytska and her family survived by cooking on a makeshift stove and drinking well water under near-constant bombardment.

“I was scared, then I got used to it,” her 14-year-old daughter Vladyslava said.

A defender of the steel plant said Russian forces resumed shelling the plant Sunday as soon as the civilians were evacuated.

Denys Shlega, commander of the 12th Operational Brigade of Ukraine’s National Guard, said in a televised interview Sunday night that several hundred civilians are still trapped alongside nearly 500 wounded soldiers and “numerous” dead bodies.

“Several dozen small children are still in the bunkers underneath the plant,” Shlega said.

As many as 100,000 people may still be in Mariupol, including an estimated 2,000 Ukrainian fighters beneath the sprawling, Soviet-era steel plant — the only part of the city not occupied by the Russians.

A siege of Mariupol since the early days of the war has trapped civilians with scarce access to food, water, medicine and electricity. A Russian airstrike hit a maternity hospital early in the conflict, and hundreds of people were reported killed when a theater was bombed.

The city, which had a pre-war population of more than 400,000, is a key Russian target because its capture would deprive Ukraine of a vital port, allow Moscow to establish a land corridor to the Crimean Peninsula, which it seized from Ukraine in 2014, and free up troops for fighting elsewhere in the Donbas, now Russia’s main focus.

A Ukrainian officer at the steel plant urged groups like the U.N. and the Red Cross to also ensure the evacuation of wounded fighters at the plant, though he acknowledged that reaching some of the injured is difficult.

“There’s rubble. We have no special equipment. It’s hard for soldiers to pick up slabs weighing tons only with their arms,” Sviatoslav Palamar, deputy commander of the Azov Regiment, told the AP in an interview. “We hear voices of people who are still alive” inside shattered buildings.

U.N. humanitarian spokesman Saviano Abreu said civilians arriving in Zaporizhzhia, about 140 miles (230 kilometers) northwest of Mariupol, would get immediate support, including psychological services. A Doctors Without Borders team was waiting for the U.N. convoy at a reception center for displaced people in the city.

In his nightly address Sunday, Zelenskyy accused Moscow of waging “a war of extermination,” saying Russian shelling had hit food, grain and fertilizer warehouses, and residential neighborhoods in the city of Kharkiv, in the Donbas and other regions.

More than 350,000 people have been evacuated from combat zones thanks to humanitarian corridors pre-agreed with Moscow, he said, adding the “organization of humanitarian corridors is one of the elements of the negotiation process which is ongoing.”

In Zaporizhzhia, residents ignored air raid sirens to visit cemeteries on Sunday, 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.”

Meanwhile, Russian forces embarked on a major military operation to seize the Donbas, Ukraine’s eastern industrial heartland, after failing to capture Kyiv.

A full picture of battle unfolding in eastern Ukraine is hard to capture. The fighting makes it dangerous for reporters to move around, and both sides have introduced tight restrictions on reporting from the combat zone.

Western officials say Russia is advancing slowly in its eastern offensive and has captured some villages, but is inflicting heavy civilian casualties through indiscriminate bombing. Ukrainian forces are fighting their offensive village-by-village while civilians flee airstrikes and artillery shelling.

The British Defense Ministry said in a daily briefing Monday that it believes more than a quarter of all the fighting units Russia has deployed in Ukraine are now “combat ineffective” — unable to fight because of loss of troops or equipment.

The British military believes Russia committed over 120 so-called “battalion tactical groups” into the war since February, which represents 65% of all of Moscow’s combat strength.

Ukraine’s military claimed Monday to have destroyed two small Russian patrol boats in the Black Sea. Drone footage posted online showed what the Ukrainians described as two Russian Raptor boats exploding after being struck by missiles.

The AP could not immediately independently confirm the strikes.

Hundreds of millions of dollars in military assistance has flowed into Ukraine during the war, but Russia’s vast armories mean Ukraine still needs massive support. Zelenskyy has appealed to the West for more weapons, and tougher economic sanctions on Russia.

U.S. House Speaker Nancy Pelosi and other U.S. lawmakers visited Zelenskyy on Saturday to show American support.

European Union energy ministers were meeting Monday to discuss a new set of sanctions, which could include restrictions on Russian oil — though Russia-dependent members of the 27-nation bloc including Hungary and Slovakia are wary of taking tough action.