Exodus of refugees, collapsing fertility and war deaths, reportedly depleted Ukrainian population by around 25 percent.

Ukraine’s population has declined by around 10 million people, or about a quarter, since the start of Russia’s full-scale invasion in 2022, according to the United Nations.

The number of Ukrainians living in the country has diminished due to the exodus of refugees, a collapse in fertility, and war deaths, Florence Bauer, the Eastern Europe head of the UN Population Fund, said on Tuesday.

The invasion has accelerated an already evident population decline that began before the war, the UN agency said. That number drop matches a trend seen across much of Eastern Europe, but the conflict has worsened the situation.

The largest deterioration in Ukraine’s population is due to the 6.7 million refugees now living abroad, primarily in Europe. War deaths are also a significant factor.

“It’s difficult to have exact numbers, but estimates range around tens of thousands of casualties,” Bauer said.

“The birth rate plummeted and is currently at around one child per woman, which is one of the lowest in the world,” the UN official added.

A fertility rate of 2.1 children per woman is needed to maintain a stable population.

Accurate population data for Ukraine won’t be available until after the conflict ends, and a complete census can be conducted, Bauer noted.

Ukraine, which had a population of over 50 million when the Soviet Union collapsed in 1991, has, like almost all its Eastern European and Central Asian neighbours, undergone severe population decline in recent years.

In 2021, ahead of the Russian invasion, the country had around 40 million people.

Russia, meanwhile, with a pre-war population of over 140 million, has also seen its population deteriorate since it invaded Ukraine.

The country recorded its lowest birth rate since 1999 in the first six months of this year; a development that the Kremlin called “catastrophic”.