Ukraine's president was preparing to make a direct appeal for more help in a rare speech by a foreign leader to the U.S. Congress, even as Russia continued its bombardment of the Ukrainian capital Wednesday.

In the war's third week, Ukrainian President Volodymyr Zelenskyy suggested there was still some reason to be optimistic that negotiations with the Russian government might yet yield an agreement.

Previewing his speech to the U.S. Congress, Zelenskyy thanked President Joe Biden and "all the friends of Ukraine" for $13.6 billion in new support. He appealed for more weapons and more sanctions to punish Russia and repeated his call to "close the skies over Ukraine to Russian missiles and planes."

Zelenskyy said Russia's demands were becoming "more realistic" after their delegations met Tuesday via video. The sides were expected to speak again later Wednesday.

"Efforts are still needed, patience is needed," he said in his video address to the nation. "Any war ends with an agreement."

He said Russian forces had been unable to move deeper into Ukrainian territory but had continued their heavy shelling of cities.

Developments on the diplomatic front and on the ground occurred as the number of people fleeing Ukraine amid Europe's heaviest fighting since World War II eclipsed 3 million.

Zelenskyy said 28,893 civilians were able to flee through nine humanitarian corridors in the past day although the Russians refused to allow aid into Mariupol.

Shrapnel from an artillery shell slammed into a 12-story apartment building in central Kyiv on Wednesday, obliterating the top floor and igniting a fire that sent plumes of smoke over the area, according to a statement and images released by the Kyiv emergencies agency. The neighboring building was also damaged. The agency reported two victims, without saying if they were injured or killed.

Also, a powerful explosion thundered overnight in Kharkiv that was heard across the eastern city.

In addition to airstrikes and shelling by ground forces, Russian naval ships fired overnight on a town south of Mariupol on the Azov Sea and another near Odesa on the Black Sea, according to local officials.

Russian forces have intensified fighting in the Kyiv suburbs, notably around the town of Bucha in the northwest and the highway leading west toward Zhytomyr, the head of the Kyiv region Oleksiy Kuleba said. He said Russian troops are trying to cut off the capital from transport arteries and destroy logistical capabilities even as they plan a wide-ranging attack to seize Kyiv.

Twelve towns around Kyiv are without water and six without heat.

Russia has occupied the city of Ivankiv, 80 kilometers (50 miles) north of Kyiv, and controls the surrounding region on the border with Belarus, Kuleba said.

Across the Kyiv region, he said, "Kindergartens, museums, churches, residential blocks and engineering infrastructure are suffering from the endless firing."

A senior U.S. defense official, speaking on the condition of anonymity to discuss the Pentagon's assessment, said Tuesday the Russians were using long-range fire to hit civilian targets inside Kyiv with increasing frequency but that their ground forces were making little to no progress around the country. The official said Russian troops were still about 15 kilometers (9 miles) from the center of the capital.

Before Tuesday's talks with Ukrainian officials, Russian Foreign Minister Sergey Lavrov said Moscow would press its demands that Ukraine drop its bid to join NATO, adopt a neutral status and "demilitarize."

In a statement that seemed to signal potential grounds for agreement with Moscow, Zelenskyy told European leaders gathered in London that he realizes NATO has no intention of accepting Ukraine.

"We have heard for many years about the open doors, but we also heard that we can't enter those doors," he said. "This is the truth, and we have simply to accept it as it is."

NATO does not admit nations with unsettled territorial conflicts. Zelenskyy has repeatedly said he realizes NATO isn't going to offer membership to Ukraine and that he could consider a neutral status for his country but needs strong security guarantees from both the West and Russia.

The U.N. said close to 700 civilians in Ukraine have been confirmed killed, with the true figure probably much higher.

On a day when thousands managed to leave Mariupol, Russian troops seized the city's largest hospital, regional leader Pavlo Kyrylenko said. He said the troops forced about 400 people from nearby homes into the Regional Intensive Care Hospital and were using them and roughly 100 patients and staff as human shields by not allowing them to leave.

Kyrylenko said shelling had already heavily damaged the hospital's main building, but medical staff have been treating patients in makeshift wards in the basement.

Doctors from other Mariupol hospitals made a video to tell the world about the horrors they've been seeing. "We don't want to be heroes and martyrs posthumously," one woman said. She also said it's insufficient to simply refer to people as the wounded: "It's torn off arms and legs, gouged out eyes, bodies torn into fragments, insides falling out."

The employee of Russian state television who was arrested after interrupting a live news program by protesting the war in Ukraine was fined about about $270, but still could face a prison sentence.

"These were very difficult days of my life because I literally went two full days without sleep, the interrogation lasted for more than 14 hours and they didn't allow me to contact my family and close friends, didn't provide any legal support," Marina Ovsyannikova said after she was released.

Ovsyannikova, an employee of Channel 1, walked into the studio during Monday's evening news show with a poster saying "stop the war, don't believe the propaganda, they are lying to you here." In English, it said "no war" at the top of the poster and "Russians against the war" at the bottom.

Two journalists working for Fox News were killed in a vehicle hit by fire Monday on the outskirts of Kyiv. Fox identified them as video journalist Pierre Zakrzewski and Ukrainian journalist Oleksandra "Sasha" Kuvshynova, who was helping Fox crews navigate the area. Another journalist was killed Sunday in Ukraine.

On Tuesday, the leaders of three European Union countries - Poland, the Czech Republic and Slovenia - visited Kyiv in a bold show of support amid the danger.

Fighting has intensified on Kyiv's outskirts, and the mayor imposed a curfew through Thursday morning. Tuesday's artillery strikes hit the Svyatoshynskyi district of western Kyiv.

"Yesterday we extinguished one fire, today another. It is very difficult," a firefighter who gave only his first name, Andriy, said outside a 15-story apartment building that was hit, tears falling from his eyes. "People are dying, and the worst thing is that children are dying. They haven't lived their lives and they have already seen this."

From The Associated Press