Smugglers test migrant Black Sea route to Romania

"It is a bit early to talk about the route reopening, but it could be that the smugglers are testing how it works - that is a possibility," said a spokeswoman from the Warsaw-based agency.

"We think it might just be testing. We've been watching this route since 2011," she said.

The Romanian coastguard had announced over the weekend that some 200 refugees from Iran and Iraq had arrived by boat at the port of Mangalia, Romania. One of the boats was carrying 36 children.

Eugenio Ambrosi, the Brussels office regional director of the International Organization for Migration, also said on Tuesday that the arrivals in Romania are "a clear indication" that traffickers and smugglers are looking into alternatives.

Romania is not a part of the passport-free Schengen travel area. However, with the Western Balkan route closed and people getting stuck at the Greek islands, some may see Romania as a more attractive option.

The arrivals in Romania also come amid a relative daily increase in people arriving on the Greek islands, when compared to last year.

An average of some 93 per day are said still to be landing on the Greek coasts, with many ending up in lengthy asylum procedures and in poor conditions.

Almost 1,900 have been sent back to Turkey since the EU and Ankara's migrant deal was agreed to in early 2016.

These returns may see a dramatic increase should the Greek council of state plenary rule against pending cases filed by Syrians on whether Turkey is safe for refugees.

Those cases are still pending, while political pressure mounts among Greek authorities to fast track the appeals process.