Russia on Friday claimed its troops have “completely liberated” the Azovstal steel plant in Mariupol — the final holdout of Ukrainian resistance in the otherwise Russian-occupied southern city.

CNN cannot independently verify that all Ukrainian troops have left the steel plant.

Ukraine is yet to confirm Russia’s claims, which, if true, would mark a symbolic military victory for Moscow.

Here’s what you need to know:

The siege of Mariupol: The strategically important port city was one of the first to come under Russian attack after Moscow’s invasion began on Feb. 24. By early March, it had been surrounded by Russian forces, leaving residents facing dire shortages of food and water — and constant bombardment that hit a maternity hospital and a theater where civilians were sheltering.

The plant: By mid-April, most of the last Ukrainian defenders were fighting to hold Russian forces back from the Azovstal steel plant — which had also become a shelter for as many as 1,000 civilians, including some seriously injured who were stranded without medical care.

In late April, Russia claimed it had achieved the “liberation” of Mariupol — which Ukrainian President Volodymyr Zelensky denied, saying soldiers were still resisting in the city.

Evacuation attempts: Evacuations of civilians from Azovstal began on May 1. On May 16, Ukraine’s military said its forces had completed their “combat mission” at the steel plant, with hundreds of soldiers evacuated from the facility.

Hundreds of Ukrainian soldiers evacuated from the plant were taken to a pre-trial detention center, while the severely injured were receiving medical treatment, according to the Russian Defense Ministry.

Ukraine said it expects to carry out an exchange of Russian prisoners of war for the severely injured soldiers.

The situation on the ground: If true, Russia’s claim on Friday would suggest the entire city of Mariupol has fallen to Russian control after nearly three months of brutal fighting.

A spokesperson from the Russian Defense Ministry claimed the “last group of 531 militants surrendered” in the plant. Earlier, the Ukrainian commander of the Azov regiment had issued an order for soldiers to preserve their “life and health … and stop defending the city.”

Videos posted online appear to show the remaining Azov fighters walking out of the steel plant. CNN cannot independently verify the number of fighters left in the plant.

Russian gains: If confirmed, the fall of the Azovstal steel plant means Russian forces are in full control of Mariupol, paving the way for them to establish a land corridor between Russia and the annexed territory of Crimea.

The symbolic victory would also secure a key port on the Sea of Azov for Russia and release Russian troops to fight on the front lines of the war in the Donbas region.