Over 20,000 migrants have travelled to Europe by sea in the first 122 days of 2018, according to the UN Migration Agency.

The International Organization for Migration (IoM) recorded 22,439 sea arrivals in total, with about 42 per cent arriving in Italy, 38 per cent in Greece, and 20 per cent in Spain — where illegal, seaborne migration has been steadily rising, as controls in first Greece and then Italy have tightened.

People-smugglers had also begun to exploit the dangerous Black Sea route to Europe for the first time since 2014 last summer, with almost 500 making landfall in Romania in a month over August-September — but the latest IoM bulletin does not discuss how the situation is developing on this particularly treacherous front.

Despite the slow but steady rise in Spanish landings, monthly arrivals are down significantly on previous years overall, with Greek landings peaking at over 815,000 in 2015, and Italian landings peaking at over 180,000 in 2016.

These numbers were reduced by the negotiation of a multi-billion euro deal with the Islamist government of Turkey to step up containment efforts in the Aegean, and Italian initiatives to crack down on NGO ‘rescue’ ships and encourage the Libyan Coast Guard to intercept smuggler-boats and turn them around.

However, the governments of some Western European countries believe the situation could be worse than the IoM numbers suggest, with EU border states allowing many migrants to pass through their territory unrecorded.

The EU does not permit member-states to deport illegal migrants to the last safe country they passed through — from the United Kingdom to France in the case of Calais migrants, for example — mandating that they can only be sent back to the first EU country they entered.

This creates an incentive for EU border states not to register migrants so that Western European countries cannot discover their original point of entry and send them back.

Dutch migration minister Mark Harbers has complained that 95 per cent of illegal migrants in the Netherlands have arrived from other EU members, but two-thirds of them have never been registered elsewhere.

Italy and Greece Accused of Waving ‘Irregular Migrants’ Through Borders https://t.co/bXFThFEw7v — Breitbart London (@BreitbartLondon) May 4, 2018

There is also serious concern that Greece — still struggling to deal with thousands of migrants who remain encamped on its Aegean islands — now faces another major influx not from the sea, but overland.

The country’s land border with Turkey in East Thrace is not covered by the controversial EU-Turkey deal, and people-smugglers have now begun to exploit it in earnest.

The IoM told Breitbart London that land crossings have increased from 393 in January, 425 in February, and 1,327 in March.

Separate UN Refugee Agency (UNHCR) figures show a marked spike to almost 3,000 in April, with the mayor of one Greek border town saying “things are on the verge of spinning out of control” and “far more are coming than are actually being registered”.

Turkey has threatened to open the floodgates to the European Union on several occasions if a series of demands on money, visa-free travel, and progress on its EU membership bid are not met, and its relationship with Greece, in particular, appears to be deteriorating rapidly.

Follow Jack Montgomery on Twitter: @JackBMontgomery