Russian forces have killed thousands in Mariupol, could use chemical weapons, warns Ukrainian President Zelenskyy

"Mariupol has been destroyed, there are tens of thousands of dead, but even despite this, the Russians are not stopping their offensive," President Volodymyr Zelenskyy said in a video address to South Korean lawmakers without providing more details.

KYIV: Ukraine has said that tens of thousands of people have likely been killed in Russia`s assault on the southeastern city of Mariupol while the country`s rights ombudswoman accused Russian forces in the region of torture and executions.

News agency Reuters has confirmed widespread destruction in Mariupol but could not verify the alleged crimes or the estimate of those killed in the strategic city, which lies between Russian-annexed Crimea and eastern areas of Ukraine held by Russian-backed separatists.

"Mariupol has been destroyed, there are tens of thousands of dead, but even despite this, the Russians are not stopping their offensive," President Volodymyr Zelenskyy said in a video address to South Korean lawmakers without providing more details.

The Ukrainian President also said in his daily video address late on Monday that Russia forces could use chemical weapons in Ukraine, but he did not say that chemical weapons have been already used.

There were unconfirmed reports on Monday suggesting that chemical weapons were used in the besieged southern Ukrainian port of Mariupol.