The United Nations Secretary-General Antonio Guterres said on Monday Russia's ongoing military operation "will have no winners, only losers."

Guterres made the remarks as he briefed journalists on the situation in Ukraine.

"The impact on civilians is reaching terrifying proportions. Countless innocent people, including women and children, are being killed," he said.

The UN chief also announced $40 million in humanitarian assistance to Ukrainians affected by the operation.

"As millions of people in Ukraine face hunger and dwindling supplies of water and medicine, I am announcing today that the United Nations will allocate a further $40 million from the UN's emergency fund to ramp up vital assistance to reach the most vulnerable," he said.

The military operation is on its 19th day.

The UN said earlier that the number of refugees who have fled Ukraine since the Russian military operation began on February 24 topped 2.8 million, making it the largest refugee exodus in Europe since World War II.

Ukrainian presidential adviser Mykhailo Podolyak said that a new round of Russia-Ukraine virtual talks took a technical pause until Tuesday, as both sides seek a solution to the situation.