The number of people found to be illegally present in the European Union increased by 22% to reach nearly 700,000 in 2021, according to European statistics office data released on Thursday.
Syrians made up the largest number, followed by Algerians and Afghans. The number of Afghans increased by about 55% compared with 2020, following the takeover of the country by the Taliban in August.
Men accounted for about 87% of the total number reported by Eurostat, with more than half aged 18 to 34.
In all, Eurostat said that 681,200 non-EU individuals were found to be illegally present in the bloc's 27 countries in 2021, 123,700 more than the previous year but down 67% from a peak in 2015, when more than a million people from Syria and other conflicts reached the EU.
The number included those who entered the bloc illegally as well as those who overstayed the time allowed.
France reported the largest number, at 215,200, a 107% jump compared with 2020.
It is followed by Hungary and Germany. Together the three countries accounted for nearly 70% of all illegally present non-EU citizens in the bloc.
Ukrainians made up the biggest number of citizens denied entry to the EU in 2021, with about 50,200 rejections out of 139,000.
Rejected Ukrainian citizens sought to cross land borders into Hungary, Poland and, to a lesser extent, Romania.
The number of non-EU citizens presented with orders to leave a member state decreased by around 14% from 2020, with around 37% of orders issued by France, more than any other member state.
While more than half were enforced returns, 47% left the territory voluntarily, Eurostat said.
Overall, the majority of denied entries were due to the person's purpose and conditions of stay not being justified, Eurostat said, but also in 29% of cases because the person was considered a public threat.