Russia is dropping bunker-buster bombs on a Mariupol steel plant where Ukrainian civilians are hiding

businessinsider.com: Russia is dropping bunker-buster bombs on a steel plant in the southeastern Ukrainian city of Mariupol where soldiers and citizens have been hiding, a Ukrainian military commander said.

Denys Prokopenko, the commander of the Ukrainian National Guard's Azov Regiment, said on Monday that Russia had started dropping bombs on the Azovstal Iron and Steel Works plant, the Associated Press reported.

Prokopenko said his troops were there alongside civilians.

The plant includes underground tunnels, and Mariupol's city council said on Telegram on Monday that up to 1,000 citizens were also hiding there.

Bunker busting bombs are designed to hit targets that are deep underground and to penetrate through thick defenses.

Prokopenko said Russian troops were aware that civilians were hiding there, and firing anyway: "Russian occupational forces, and their proxy ... know about the civilians, and they keep willingly firing on the factory," he said.

Russia on Tuesday told troops in the plant to lay down their arms by midday Moscow time if they wanted to live. "All who lay down their arms are guaranteed to remain alive," Russia's defense ministry said, Reuters reported.

Mikhail Vershinin, head of the Donetsk regional patrol police, said on Sunday that children were among the civilians at the plant, Politico reported. Mariupol is in Ukraine's Donetsk region.

The port city of Mariupol has been one of the most-hit parts of Ukraine since Russia's invasion began on February 24. Seizing Mariupol would give Russia effective control over the land route from Russian-controlled Crimea and the eastern Donbas region, where Russian troops started attacking early Tuesday.

Ukrainian officials estimate that around 21,000 civilians have been killed in the city, and Ukrainian Foreign Minister Dmytro Kuleba said on Sunday: "The city doesn't exist anymore. The remaining of the Ukrainian army and large group of civilians are basically encircled by the Russian forces."

Some of those remaining in the city are in the steel plant, which may be the last pocket of resistance in the city.

Russia has ordered Ukrainian soldiers left in Mariupol to surrender, but they have refused.

Yan Gagin, an advisor to the Russia-backed separatist forces in Donetsk, told Russian media outlet Ria Novosti that the steel plant is "basically another city" under Mariupol, and that it was built to withstand bombings.