Ireland's representative on the UN Security Council has described Russia's invasion of Ukraine as "abhorrent", with conflict-related sexual violence being used as a weapon in the ongoing war.

Ambassador Geraldine Byrne Nason was addressing the Security Council, which has been meeting to discuss the use of such violence in the war.

UN human rights agencies say they have corroborated 124 cases of alleged sexual violence committed in Ukraine.

However, the actual number of sexual crimes in the war was likely to be significantly higher, according to Pramila Patten, Special Representative of the UN Secretary-General on Sexual Violence in Conflict.

"We've been watching the fallout of this abhorrent war, civilians attacked and killed, schools and hospitals targetted, mass displacement and family separation, conflict related sexual violence and human trafficking," Ambassador Byrne Nason said.

"Let me be clear: This is no special military operation, this is an illegal war causing intentional damage and suffering."

She said so far 15 million people, the vast majority of them women and children, had been forced to leave their homes, with some of them vulnerable to the threat of human trafficking.

"The speed and scale of the displacement is unheard of in modern times," Ambassador Byrne Nason said.

Addressing the same meeting, Natalia Karbowska, Co-founder and Director on Strategic Development at the Ukrainian Women's Fund, said: "Russia is using sexual violence and rape as a terror to control civilians in the temporary occupied territories.

"Although the full scale of conflict related sexual violence is not yet known, human rights activists and law enforcement agencies estimate that hundreds of cases have been committed not just against women and girls, but also men and boys and people of other gender identities and of all ages.

"So, I have a question. Russia is using terror against civilians in Ukraine. There is a lot of evidence to prove this. Why it is still in the UN Security Council? How it is possible that it participates in the UN peacekeeping operations?"

Russia has claimed no evidence has been provided of such crimes.

Vassily Nebenzia, Russia's Permanent Representative to the UN, said: "The ratcheting up of accusations against Russian service personnel committing crimes of a sexual nature... has become a favourite tactic of the Kyiv regime."

He said Russian soldiers were being portrayed by Western political scientists "as beasts and coarse barbarians".

Ukraine has accused Russia of trying to hide the evidence of such crimes, including the burning of the bodies of victims.