Ukraine says its troops are preparing for a "last battle" against Russian forces in the besieged port city of Mariupol.
The city in southern Ukraine has been the scene of intense fighting following the Russian invasion.
On Monday, Ukrainian forces warned that their ammunition in the city is running out and that they will either be subject to "death" or "captivity".
Earlier, Ukraine said that Russian forces had left more than 1,200 bodies in mass graves in towns and villages around the capital, Kyiv.
Watch: Ukraine says it has found more than 1,200 bodies near Kyiv
On Monday, the 36th marine brigade of the Ukrainian armed forces said it had been defending Mariupol for 47 days from Russian attack.
In a statement posted on Facebook, it said: "Today will probably be the last battle, as the ammunition is running out.
"It’s death for some of us, and captivity for the rest.
"The mountain of wounded makes up almost half of the brigade. Those whose limbs are not torn off return to battle.
"The infantry was all killed and the shooting battles are now conducted by artillerymen, anti-aircraft gunners, radio operators, drivers and cooks. Even the orchestra."
The marines said they are doing "everything possible and impossible" to keep control of the city, but that they have been pinned down by the Russians.
The brigade said "the enemy gradually pushed us back" and "surrounded us with fire and is now trying to destroy us" in the the city's port and iron and steel works.
The marines said there had been a lack of support from Ukraine's military leadership "because we've been written off".
On Monday, Ukraine's president, Volodymyr Zelensky, said tens of thousands of people had likely been killed in Mariupol.
Speaking via video link to South Korea's parliament, he said: "Mariupol has been destroyed, there are tens of thousands of dead, but even despite this, the Russians are not stopping their offensive."
The UK has expressed fears that Russian president Vladimir Putin’s forces could use white phosphorus (WP) munitions in the bombardment of Mariupol.
A British defence intelligence assessment said WP had already been used by Russia in the Donetsk region of eastern Ukraine.
White phosphorus is used for illumination at night or to create a smokescreen, but when it is deployed as a weapon it causes horrific burns.
The intelligence assessment published by the Ministry of Defence on Monday said: “Russian forces’ prior use of phosphorus munitions in the Donetsk Oblast raises the possibility of their future employment in Mariupol as fighting for the city intensifies.”
The MoD said Russian forces had continued shelling in the Donetsk and Luhansk areas of eastern Ukraine, but Kyiv’s troops had repulsed “several assaults”.
Watch: Inside the Mariupol theatre where hundreds killed by Russian shelling