Women with their children after fleeing from Ukraine to Romania, Poland, following Russia's invasion. Reuters / AFP / AP

Fresh numbers from the International organisation for Migrantion (IOM) showed on Tuesday that more than three million people have now fled Ukraine. Nearly half of them are thus children.

"On average, every day over the last 20 days in Ukraine, more than 70,000 children have become refugees," James Elder, spokesman for the UN children's agency UNICEF, told reporters in Geneva.

That amounts to around 55 every minute, "so almost one per second," he said, stressing that "this crisis in terms of speed and scale is unprecedented since World War II."

Elder warned that "like all children driven from their homes by war and conflicts, Ukrainian children arriving in those border countries are at significant risk of family separation, of violence, of sexual exploitation and trafficking.

"They're in desperate need of safety, stability and child protection services," he said.

The United Nations chief warned that Russia’s war on Ukraine is holding "a sword of Damocles” over the global economy, especially poor developing countries that face skyrocketing food, fuel and fertiliser prices and are now seeing their breadbasket "being bombed.”

Guterres told reporters that "Russia and Ukraine represent more than half of the world’s supply of sunflower oil and about 30 per cent of the world’s wheat” and that "grain prices have already exceeded those at the start of the Arab Spring and the food riots of 2007-2008.”

He told reporters that 45 African and least developed countries import at least one-third of their wheat from Ukraine and Russia, and 18 of them import at least 50%.

These countries include Egypt, Congo, Burkina Faso, Lebanon, Libya, Somalia, Sudan and Yemen, he said.

"All of this is hitting the poorest the hardest and planting the seeds for political instability and unrest around the globe,” Guterres warned.

Guterres warned on Monday that the world must act to prevent a "hurricane of hunger and a meltdown of the global food system" following Russia's invasion of Ukraine.

The secretary-general told reporters in New York that the war risks sparking far-reaching consequences for the global food supply that will have a devastating impact on the poorest.

"This war goes far beyond Ukraine. It is also an assault on the world's most vulnerable people and countries," Guterres said.

Agencies