Media playback is unsupported on your device Media caption Activists who've fled Raqqa have been talking to BBC Newsnight

Political activists in northern Syria have been forced to flee after attempting to defy the growing power of al-Qaeda in the region.

A citizens' protest movement has been challenging the jihadist group, the Islamic State in Iraq and the Levant (ISIS), an affiliate of al-Qaeda, after its fighters attacked churches in the city of Raqqa.

But activists who have fled to Turkey told BBC Newsnight that many had been arrested, beaten or kidnapped by ISIS in retaliation.

Raqqa, a city currently sheltering nearly a million people, is now under the full control of the group.

One of the activists, photographer Mezar Matar, said: "I saw many people who had signs of lashes on their bodies after being released from an ISIS prison."

They are the new dictators, just like Bashar al-Assad but dressed in black Mezar Matar, Activist who fled Raqqa

He said his brother, Muhammed Nour, had disappeared after filming a battle in Raqqa between ISIS and a brigade loyal to the Western-backed Supreme Military Council of the Free Syrian Army (FSA).

He believed Muhammed had been kidnapped by the jihadists.

Another activist, who asked not to be named for her own safety, said she and her sister, also involved in the protest movement, had fled after being fired at by ISIS gunmen.

"Seven or eight men with explosive belts surrounded my sister. Some said: 'Knife her.' Some said: 'Shoot her.' They tore down her banner that said 'Christians and Muslims are one', and told her she was an infidel," the activist said.

The protests started in September after jihadists raised their black flag over a church in Raqqa and turned it into their headquarters.

Image caption The black flag was flown from Raqqa's Armenian Catholic Church of the Martyrs

"Two carloads of armed fighters went onto the roof of the church. They broke the bell with hammers, and threw one of the crosses down into the street. They tried to break it, but it was iron," the activist said.

Activists filmed protesters carrying the cross through the streets shouting "Shame! Shame!" and calling for Muslim-Christian unity.

'New dictators'

Earlier this year, Raqqa became the first provincial capital in Syria to fall fully under rebel control.

Image caption A statue of the late President Hafez al-Assad was toppled after Raqqa's capture

But after only two months when control was shared by SMC-aligned and jihadist fighters, it was taken over in May by ISIS.

They marked the moment by publically executing three men they said were Alawites, members of the same heterodox Shia sect as President Bashar al-Assad.

Now Raqqa, its population swollen by displaced families, may be the largest city in the world ever to be controlled by al-Qaeda.

Mr Matar said: "They banned the sale of alcohol, they tried to close cafes where boys and girls sit together, they banned street theatre, cinema, bright colours, and forced women to wear Islamic dress.

"They are the new dictators, just like Bashar al-Assad, but dressed in black. Only the colour has changed."

Image caption Raqqa in northern Syria may be the largest city in the world to be controlled by al-Qaeda

Smaller but better funded than other rebel groups, ISIS has historically been made up of foreign jihadists from Arab countries - particularly Iraq, but also Libya, Tunisia, and Saudi Arabia - Russia's north Caucasus, and Europe.

But activists from Raqqa said it was now attracting more and more Syrian recruits.

In the last few months, ISIS has made significant advances, largely at the expense of the FSA, and controls a wide swathe of northern Syria close to the Turkish border.

See more from Tim Whewell on Newsnight on Wednesday 13 November 2013 at 2230 on BBC Two, and then afterwards on the BBC iPlayer and Newsnight website.