The Russian attacks on the steel plant area in Mariupol on Tuesday evening, together with intense attacks in recent days, are said to have leveled parts of the Azovstal steel plant.
According to an adviser to the Ukrainian president, the Russian forces have used deep-penetrating bombs, or as they are sometimes also called - bunker bombs.
Has been used since World War II
Deep-penetrating aerial bombs have been used since World War II and are designed to penetrate very hard materials or deep into the ground, such as bunkers.
Today, they are as big as conventional bombs, and instead use extra charges to be able to penetrate tens of meters of, for example, concrete.
They are often precision controlled.
Corresponding weapons are found on the American side, they were used in the Gulf War, among other places.
It is an extremely thick steel pipe with explosives that can penetrate concrete, several meters depending on the type.
So this is really nasty stuff, says defense expert Joakim Paasikivi to SVT's Aktuellt.
"Been wrong for two weeks, so I dare not guess"
How long do you think Ukrainian forces will be able to hold this resistance pocket in Mariupol?
- I have been wrong for two weeks when I have said "soon", so I dare not guess.
If you can have fuel, ammunition and food, you can last a long time, provided that you are not hit by these bombs, says Joakim Paasikivi at the Swedish National Defense College.
Russia has not confirmed the weapons used in its attacks on the steelworks area, but the Defense Ministry gave the Ukrainian forces on the ground another chance to lay down their weapons on Tuesday evening, at 12 noon.