Islamic State fighters are being smuggled into Europe by gangs in the Mediterranean, an adviser to the Libyan government told the BBC.

Abdul Basit Haroun said smugglers were hiding IS militants on boats filled with migrants.

Officials in Italy and Egypt have previously warned that IS militants could reach Europe by migrant boat.

However, experts have cautioned that it is very difficult to verify or assess such claims.

Mr Haroun based his claim on conversations with smugglers in parts of North Africa controlled by the militants.

He alleged that IS was allowing the boat owners to continue their operations in exchange for half of their income.

About 60,000 people are estimated to have tried to cross the Mediterranean this year, fleeing conflict and poverty. 

In an interview with BBC Radio 5 live Investigates, Mr Haroun said IS used the boats "for their people who they want to send to Europe, as the European police don't know who is from IS and who is a normal refugee or not".

These militants often sat separately from the other migrants, he said.

Earlier this year, the EU's border control agency, Frontex, warned that it was "possible" that foreign fighters were using irregular migration routes to get into Europe.

Egypt's ambassador to the UK has warned of "boats full of terrorists" if the international community does not act, while the Italian government has expressed fears of militants infiltrating the boats, while emphasising that the boats are a humanitarian crisis.