Mariupol

Taking the Azovstal industrial district, where the marines have been holed up, would give the Russians full control of Mariupol, Ukraine's main Sea of Azov port, and reinforce a southern land corridor before an expected new offensive in the country's east.

Surrounded and bombarded by Russian troops for weeks and the focus of some of the fiercest fighting in the war, Mariupol would be the first major city to fall since Russia invaded Ukraine on 24 February.

Most people trapped in the port city are sleeping in bomb shelters to escape more than six days of near-constant shelling by encircling Russian forces that has cut off food, water, power and heating supplies, according to the Ukrainian authorities.

The civilian death toll from hostilities across Ukraine since Moscow launched its invasion on 24 February stood at 364, including more than 20 children, according to the United Nations on Sunday, with hundreds more injured.