Turkish foreign minister Mehmet Cavusoglu earlier said the suspect works for the intelligence agency of a country that is part of the US-led coalition fighting ISIS but did not identify the country, saying only that it was not the United States or a member of the European Union.
However, an Istanbul-based newspaper has reported that the spy was working for the Canadian government.
Dailysabah.com cited 'sources close to the government' as the basis of the assertion.
Mr Cavusoglu, who was interviewed on Turkish channel A Haber TV, said he had shared the information with his British counterpart - Foreign Secretary Philip Hammond.
Shamima Begum, Amira Abase, both 15, and Kadiza Sultana, 16, are thought to have reached the terror group's de facto capital Raqqa after fleeing the UK to join a friend last month.
Britain's Foreign Office had no immediate comment and a spokesman for the Metropolitan police said he had no information.
It emerged earlier this week that the three girls had paid for their flights out of the UK after stealing jewellery from their family.
Police discovered they paid the £1,000 cost of their flights from Gatwick airport to Istanbul in cash.
Before they went missing, the girls are believed to have communicated with 20-year-old Aqsa Mahmood, a notorious jihadi who left Glasgow for Syria last year.
The former medical student has become the online contact of choice for those wanting to travel to Syria and marry a militant fighter.
One of the girls, Shamima Begum, used her Twitter account to try to contact her directly, asking for her to open a private line of communication.
Friends suspect the girls were in touch with Mahmood and Islamic State recruiters via their mobile phones in the weeks before Christmas.
The girls were pictured going through security at Gatwick Airport last month, dressed in Western clothes.
They were later seen on CCTV in Turkey, dressed in burkas and waiting for a bus to take them to the border with Syria.
They are now believed to be in Raqqa, Islamic State’s stronghold and scene of some of its most barbaric atrocities.
It is thought they were staying with a British girl – believed to be a pupil from their school who went missing in December and is believed to have joined ISIS.
The 15-year-old student, the first to disappear from Bethnal Green Academy in east London, has not been identified by the authorities.
Mark Rowley, who has overall responsibility for police counter terrorism, said the three girls would not be arrested for terrorist offences if they returned to the UK.
‘We have no evidence in this case that any of the three girls are responsible for any terrorist offences,’ he said.
Over the weekend it also emerged that letters from Scotland Yard to the girls' families – explaining that the pupils would be part of the inquiry into their friend's disappearance – had been given to the schoolgirls rather than their parents.
Metropolitan Police Commissioner Sir Bernard Hogan-Howe admitted that ‘with the benefit of hindsight’ officers should have communicated directly with the families.
But he said parents had a responsibility to come forward if their teenagers betrayed any interest in extremist ideology.
However, the families refused to accept any responsibility for the teenagers' actions when they appeared before a committee of MPs earlier this week.
Instead, they spent spent more than an hour castigating police over what they claimed was a failure to inform of their children's potential radicalisation.
They were led by their lawyer Tasnime Akunjee, once the representative of a close associate of the Woolwich killers, who repeatedly demanded an apology.
He accused Scotland Yard of a catalogue of errors in its handling of the disappearance of the trio in February and their close friend in December.
The country's top police officer was later forced to apologise to the families over a misplaced letter relating to the fourth girl's disappearance.
However, senior figures, led by David Cameron, insisted parents must take responsibility and play their part in stopping the spread of militant beliefs.
'Everyone has a role to play,' said the Prime Minister.
Foreign Secretary Phillip Hammond echoed the comments saying: 'Parents have responsibilities, schools and community workers have responsibilities as well as the authorities and airports and airline operators.'
At least 22 young women, the vast majority under the age of 20, are feared to have travelled to Syria from the UK over the past 12 months.
Police said the total confirmed number of people travelling to fight is now around 700, with many more suspected of flying out undetected.
Islamic State seized large swathes of land last June, including territory close to the Turkish border.
The U.S.-led coalition is using mostly air power in an attempt to push the Sunni militant group back.
© Associated Newspapers Ltd.