The Russian army took control of the harbor city of Mariupol, but Ukrainian soldiers are still present in the area around a large steel factory called Azovstal. This is what the Ukrainian President Volodymyr Zelensky said in a response to Russian President Vladimir Putin, who said he had taken the port city. Putin also acknowledged that he did not yet own the site of the steel plant. According to the Russian president, the site would be surrounded by Russian soldiers and he sees no reason to storm the area.
Approximately two thousand Ukrainian soldiers have entrenched themselves in and under the factory. They would not be able to pass the Russian blockades unnoticed. There are also about a thousand civilians on the industrial estate. Ukrainian leader Zelensky now confirms that the Russians control most of the city. But he emphasizes that his soldiers are still present at the steel plant. He has not made any other concrete statements about whether the Russians have taken the city.
His presidential adviser Oleksiy Arestovych says the Russians realize that it is not possible to storm the Azovstal steel factory. Russia is said to have already suffered significant losses around the factory's many buildings and the underground tunnel system. "Our defenders still have it in their hands."
Zelensky also says he has offered Russia to exchange Ukrainian civilians and soldiers in Mariupol in any possible way. Russian Defense Minister Sergei Shoigu has said Ukraine has asked for negotiations over Mariupol. Putin called on Ukrainian fighters at the factory site to surrender, saying Russia would treat them with respect and would provide medical assistance to those injured. It is unclear how many soldiers are at the site, but as mentioned before, it's estimated around 2000 soldiers remain there.
Sources:
https://www.aljazeera.com/news/2022/4/21/russia-says-all-of-mariupol-liberated-apart-from-azovstal-plant
https://www.npr.org/2022/04/21/1093977767/relentless-attacks-pound-last-defenders-holed-up-in-mariupol