In total, around 1.4 million children have now fled the war in Ukraine since the Russian invasion began, according to the UN Children's Fund Unicef.

This corresponds to an average of about 55 children per minute.

- On average, more than 70,000 children have become refugees every day during the last 20 days in Ukraine.

So almost one per second, says Unicef ​​spokesman James Elder, according to news agencies.

He warns that children who cross the border are at great risk of being separated from their families.

The consequences can be that they are exposed to violence, sexual exploitation and human trafficking.

- They have a desperate need for security, stability and protection, says James Elder.

Three million

He has just spent two weeks in Lviv in western Ukraine and says that the children on the run are not crying, reports AFP.

- These are not well-behaved children, it is a sign of trauma.

In total, more than three million people have now fled Ukraine since the war began.

Most to Poland, according to the UN refugee agency UNHCR.

- We have now reached the three million mark when it comes to people leaving Ukraine, says Paul Dillon at the migration agency IOM.

In the city of Mariupol, which has been continuously subjected to extensive attacks, it is estimated that 350,000 people remain without having had the opportunity to get out.

This is despite several attempts to establish safe escape routes.

On Tuesday, 2,000 cars are said to have managed to leave the city, according to local authorities, who add that another 2,000 vehicles are waiting to leave.

Can not escape

Those who remain live in "inhumane conditions" without water, food and heat, said Petro Andriushchenko, an adviser to the city's mayor, on Ukrainian television, CNN reports.

The International Committee of the Red Cross (ICRC) describes it as "suffocating" civilians in Mariupol and having to make impossible choices when it comes to providing food for their families and themselves, writes The Guardian.

The situation is said to be similar in Izium, in eastern Ukraine.

Deputy Mayor Volodymyr Matsokin says the city has been under siege for two weeks without water, electricity, heat, food, medicine, and communications.

- The situation is no better than in Mariupol.

We have received information that those who survived the bombings are dying from illness and lack of medicine.

"We have nowhere to bury our dead," he told CNN.