Three British girls who crossed into Syria to join Islamic State were helped by a Syrian national working as an intelligence agent for one of the countries in the US-led coalition against the jihadists, the Turkish foreign minister said on Friday.

Mevlüt Çavuşoğlu unexpectedly announced the day before that Turkey had arrested an intelligence agent who had helped the teenagers.

But amid speculation about which intelligence agency was involved, the Turkish foreign minister merely said: “The person arrested by us is someone working for an intelligence agency in the coalition.”

On Friday Çavuşoğlu told reporters that the individual was a Syrian citizen. He did not elaborate.

The Turkish newspaper Milliyet reported on Friday that the individual was working for Canadian intelligence but this has been denied by Ottawa on Thursday.

Britons Kadiza Sultana, 16, Shamima Begum and Amira Abase, both 15, crossed into Syria after boarding a flight from London to Istanbul on 17 February.

The three friends then took a bus to Sanliurfa, a city in south-east Turkey close to the Syrian border. From there they are believed to have crossed the frontier.

Along with the US and EU states, Arabian peninsula nations including Saudi Arabia and Qatar have been involved in the coalition against Isis, as well as Australia and Canada.