Bulgarian Prime Minister Boyko Borisov and visiting Croatian President Kolinda Grabar-Kitarovic have discussed the migrant crisis, calling for joint effort of all countries exposed to risk.

Grabar-Kitarovic is in Bulgaria on Wednesday and Thursday.

The two leaders "have shared the thesis that migration is causing common problems and a long-term solution can only be found through joint effort among all countries affected or exposed to risk", a statement sent by the government's press office reads.

Effective control of external borders of the EU will be of key importance for handling the migrant inflow in the short- and mid-term, Borisov is reported as saying.

Croatia is part of the so-called Western Balkans migrant route which was practically closed down after the EU and Turkey struck a deal on curbing the inflow into Europe.

Bulgaria has not been in the way of most migrants from the Middle East for the past three years, but reports have emerged of intense smugglers' activity in Hungary since the western route was closed.

The two have also discussed options to improve regional cooperation, energy and transport ties, and the EU path of other Western Balkan states (among these, Croatia has so far been the only one to join the EU).