(NewsNation) — Russian ships in the sea of Azov have been shelling Mariupol from offshore over the last 24 hours, a senior U.S. defense official said Tuesday, as the battle for the city during the Russia-Ukraine War continues.

Russian forces carried on with their siege of Mariupol on Tuesday after Ukraine refused demands to surrender. The assault has cut off Mariupol’s electricity, forcing residents into a fight for survival.

The U.S. defense official speaking about the shelling in Mariupol said there are about seven Russian ships in the area, including several warships, a minesweeper and a couple landing ships.

The official added that the U.S. did not see indications that ships in the Black Sea were still firing on the coastal city of Odesa, as they did days ago.

Ukrainian President Volodymyr Zelenskyy again criticized Russia for attacking civilians, claiming they were not honoring evacuation agreements.

“We are trying to organize stable humanitarian corridors for Mariupol residents, but almost all of our attempts, unfortunately, are foiled by the Russian occupiers, by shelling or deliberate terror,” he said in his nightly video address to the nation

Zelensky also said Tuesday that there is “nothing left” undamaged in the port city of Mariupol amid Russian attacks, and that 100,000 civilians remain trapped with no food, water or medicine.

Ukrainian forces have been keeping up the fight against Russia, saying they retook a strategically important suburb of Kyiv early Tuesday, as Russian forces besieged other areas near the capital and Mariupol.

Ukrainian troops forced Russian troops out of the Kyiv suburb of Makariv after a fierce battle, Ukraine’s Defense Ministry said. The regained territory allowed Ukrainian forces to retake control of a key highway and block Russian troops from surrounding Kyiv from the northwest.

“So many of us expected that the Russians were going to fight this like we (the U.S.) would’ve fought it and they just haven’t done that. They’ve failed miserably on the operational level,” retired Army Maj. Mike Lyons said Tuesday on “NewsNation Prime.”

Despite weeks of Russian troops’ bombardment, Ukraine has so far slowed Russia’s advance almost to a halt, a Western official speaking on condition of anonymity told the Associated Press. Still, Russian troops have not been pushed back from established positions, and they still have the capability to keep up a war of attrition for some time.

The Defense Ministry said Russian forces battling toward Kyiv were able to partially take other northwest suburbs, Bucha, Hostomel and Irpin, some of which had been under attack almost since Russia’s military invaded almost a month ago.

U.S. and British officials say Kyiv remains Russia’s primary objective. The majority of Moscow’s forces remain miles from the center, but missiles and artillery have destroyed apartment buildings and a large shopping mall, killing eight people.

Russia’s invasion has driven nearly 3.5 million people from Ukraine, according to the United Nations, with an additional 6.5 million displaced inside the country. The U.N. has confirmed more than 900 civilian deaths, while saying the real toll is probably much higher. Estimates of Russian deaths vary, but even conservative figures are in the low thousands.

Beyond the terrible human toll, the war has shaken the post-Cold War global security consensus, imperiled the global supply of key crops including wheat, and repeatedly raised worries it could set off a nuclear accident. Ukraine’s natural resources minister said Tuesday that wildfires near the Chernobyl nuclear power plant in northern Ukraine have been extinguished and radiation levels in the area are within norms.

President Joe Biden, who is heading to Europe later in the week to meet with allies, suggested Monday evening that worse may be still to come.

“Putin’s back is against the wall,” Biden said. “He wasn’t anticipating the extent or the strength of our unity. And the more his back is against the wall, the greater the severity of the tactics he may employ.”

Biden is expected to announce new sanctions against Russia while in Brussels on Thursday at a special meeting of NATO.

As Russian forces try to squeeze Kyiv, talks to end the fighting have continued but failed to bridge the gap between both sides. Zelenskyy told Ukrainian television late Monday that he would be prepared to consider waiving any NATO bid by Ukraine, a key Russian demand, in exchange for a cease-fire, the withdrawal of Russian troops and a guarantee of Ukraine’s security.

Zelenskyy also suggested Kyiv would be open to future discussions on the status of Crimea, which Russia seized in 2014, and the regions of the eastern Donbas held by Russian-backed separatists.

However, U.N. Secretary-General Antonio Guterres says he saw progress in talks to end the fighting.

“From my outreach with various actors, elements of diplomatic progress are coming into view on several key issues,” he said, “enough to end hostilities now.” But he gave no further details.

As part of a series of addresses to foreign legislatures, Zelenskyy told Italian lawmakers Tuesday that Mariupol had been destroyed and urged them to strengthen sanctions against Russia, noting many wealthy Russians have homes in the country.

“Don’t be a resort for murderers,” he said in a link from Kyiv. “Block all their real estate, accounts and yachts.”

French President Emmanual Macron spoke to Putin and Zelenskyy Tuesday about terms of a potential cease-fire, but they reached no agreement.

To date, more than 8,000 people fled to safer areas Monday through humanitarian corridors, including about 3,000 from Mariupol, Deputy Prime Minister Iryna Vereshchuk said.

The number of refugees flowing into Ukraine from a primary entry point in Poland has slowed, though, to fewer than 8,00 people a day, which is more than six to seven times lower than during the height of the exodus, Przemyśl Mayor Wojciech Bakun said Tuesday.