BRUSSELS - The European Border and Coast Guard Agency, or Frontex, said Tuesday that the number of illegal border crossings into the European Union (EU) had dropped to its lowest number in four years in 2017.

According to Frontex's 2018 report released Tuesday, a total of 204,700 migrants entered the EU last year, which marked a significant decrease compared to recent years.

The fall in migration was due to the number of people reaching Europe via the Eastern, the Central Mediterranean, and Western Balkan routes having drastically decreased.

In contrast with the declines in crossings of the three major migratory routes, the number of migrants through the Western Mediterranean route has doubled since 2016, reaching a new high of more than 23,000.

As a result, the irregular migration into the EU has not returned to the situation before 2014, when figures ranged between 72,000 and 141,000 detections, the report said.

In total, African nationals accounted for almost two-thirds of irregular migrants arriving at the shores of the EU in 2017.