Turkish authorities have detained three male teenagers who left Britain planning to travel to Syria reportedly to join the Islamic State in Iraq and the Levant (ISIL), according to British police and Turkish officials.

The trio is believed to be the latest in a growing number of UK citizens trying to travel to ISIL-held territory inside Syria.

A Turkish official confirmed that the three were detained by security forces in Istanbul on Friday and were deported back to Britain on Saturday, according to the AFP news agency.

Last month, three British schoolgirls left the UK and police believe they have joined ISIL members inside Syria.

British police said on Sunday that two of the male teens detained in Turkey were 17 years old, and the third was 19.

Counterterrorism officers learned on Friday the teens had gone missing from their homes in Britain and they were thought to be travelling to Syria, police said.

"Officers alerted the Turkish authorities who were able to intercept all three males, preventing travel to Syria. They remain in detention in Turkey. The families have been kept informed of developments," the police statement said.

Turkish sources confirm

The three, who have not been named, were detained on Friday, Turkish sources told the Reuters news agency, after a tip-off from British authorities that two of them were travelling to Turkey via Spain.

Security services estimate some 600 Britons have gone to Syria or Iraq to join armed groups, including the man known as "Jihadi John" who has appeared in several ISIL beheading videos.

Authorities say Internet-based social media have made it much easier for young Britons to communicate with groups inside Syria, with many being lured to join the armed groups there.

Turkey faced criticism for not better controlling its southeastern borders, and has accused European countries of failing to prevent people seeking to join armed groups from travelling in the first place. Ankara also criticised Western states for not cooperating with it in terms of sharing intelligence.

ISIL controls swaths of territory in Syria and Iraq where it has declared an Islamic caliphate.

Source: Agencies