Russian troops started encircling it in early March.
The siege has killed thousands of civilians and unleashed a struggle for survival for trapped residents who remained there, amid relentless Russian shelling, hunger and freezing temperatures.
Russian bombardment has reduced the city to ruins, forcing civilians to hide in cellars, while access to electricity, heating, fresh water, food and medical supplies was cut.
Thousands of people have escaped further north, risking a deadly journey through the front line.
In recent days, Russian forces are thought to have pushed in further by dividing the remaining holdout of Mariupol’s defenders, according to think tank the Institute for the Study of War (ISW).
Russian television previously broadcast footage which it said showed marines giving themselves up at the giant Azovstal steel works there.
But earlier this week, an adviser to Ukraine’s president insisted that the marines had in fact broken through to connect with Ukrainian fighters of the Azov battalion.
Now, it is difficult to know with certainty how many remain, though Ukrainian President Zelensky has acknowledged that Ukrainian forces hold only a small part of the city.
Speaking at the opening ceremony of the Invictus Games in the Netherlands, Prince Harry says that the “world is united” with Ukraine.
“You know we stand with you. The world is united with you and still you deserve more,” he told the assembled crowd on Saturday.
The Ukrainian team were given special permission by President Volodymyr Zelensky to compete at the competition for injured military veterans.
Also at the Games, the Duchess of Sussex spoke of the Ukrainian team’s presence at the event, saying it had taken a lot “both physically and emotionally” for every competitor to get to the Netherlands, “not least of which for the Ukraine team, who we are all standing with.
The answer to those questions have changed dramatically in recent years as online posts document so much of what happens on the ground in war.
Open-source information – such as photos that are freely available to anyone online – have “completely transformed our way of knowing about human rights violations”, one expert says.
“We’re seeing increasingly the UN commissions of inquiry, fact-finding missions, even the International Criminal Court in the Hague, using this kind of evidence,” she explained.