Some 150,000 people entered the European Union illegally in 2018, the bloc's border agency said on Friday, the lowest figure in five years.

Migration has dominated the political agenda across the European Union in recent years and could be a crucial issue in the buildup to European Parliament elections in May.

Read more: What is the Frontex – the European Border and Coast Guard Agency?

Frontex's estimates:

Detected illegal crossings were around 25 percent lower in 2018 than in 2017 and 92 percent below 2015, the height of the migration crisis.

Spain replaced Italy as the border country that received the most illegal immigrants, taking in some 57,000 people. That was double the number registered in 2017.

23,000 illegal immigrants arrived in Italy, a fall of 80 percent compared to 2017.

Illegal arrivals increased through Greece and Cyprus, with a total of 56,000 people entering the EU via those two countries.

Most arrivals came from Afghanistan, Syria or Iran and were men. Only 18 percent of illegal arrivals were women. One-in-five told officials they were under the age of 18.

Read more: EU's Frontex warns of new migrant route to Spain

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Why are arrivals down? Deals between the EU and transit countries such as Turkey and Libya to keep migrants from crossing into the bloc partially account for the fall in arrivals, Shoshana Fine from the European Council on Foreign Relations (ECFR) told DW. Increased investment in the bloc's border security and the growth in anti-migration sentiment and policies in many EU countries, particularly Italy, also explains the fall, she said.

Preliminary data: The figures represent detected border crossings. The same person could be registered multiple times if they crossed the border into the EU several times at different locations.

Election year: Populist parties have exploited migration to bolster their influence in Germany, Italy and Austria in recent years and are expected to continue doing so in the run-up to the European Parliament elections in May.

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