Compared to the pre-pandemic 2019, the number rose by 36%, and compared to 2020, by 57%, the agency said.
The largest number of illegal border-crossings was registered on the Central Mediterranean route, over 65,000, a jump of 83% compared to 2020.
It is followed by the Western Balkan route, which saw over 60,000 illegal border-crossings, 125% more than in 2020.
The Eastern Mediterranean and the Western Mediterranean route saw an increase of 0.5% and 6% respectively.
A new route, which has not been used before, on eastern borders with Belarus, nearly 8,000 illegal border-crossing were recorded, which is a rise of 1,069%.
In 2021, most of the people detected crossing the border illegally were Syrians, followed by Tunisians, Moroccans, Algerians and Afghans.
As in 2020, women accounted for less than 10% of illegal migrants, a significant drop in their percentage compared to 2019, according to Frontex. The share of minors remained largely the same.
On the Central Mediterranean route, most of the illegal migrants were Tunisians, followed by Egyptians, whose number increased seven times compared to 2020, and then migrants from Bangladesh, Algeria and Morocco.
On the Western Balkan route, the number of illegal border-crossings had been rising until September last year, and then it fell slightly.
Most of those detected crossing the border illegally were in the area before, and they have been repeatedly trying to enter the EU territory and continue to their desired destination, Frontex said.
