A Syrian journalist who was shot in the head by Islamic State group in southern Turkey died in hospital on Tuesday, activists said.

Hours before Mohammed Zaher al-Shurqat died from his wounds, IS claimed responsibility for Sunday's attack in the town of Gaziantep via a website.

Syrian activist Assaad al-Achi, who also lives in Gaziantep, confirmed the journalist's death, as did fellow activist Ibrahim al-Idelbi, who also lives there.

"This is a threat to all free thinkers who are fighting extremism and living in Turkey," Idelbi told AFP via the Internet.

Many Syrian journalists, activists and opposition figures who fled the country's five-year civil war use Gaziantep as a base, but it has become an increasingly dangerous location for them.

In a statement posted on IS-affiliated Amaq news agency, the jihadist group claimed responsibility for shooting Shurqat.

It said that "a covert unit" opened fire on him, calling Shurqat "a presenter known to host programmes opposing the Islamic State".

A Syrian activist who produced documentaries hostile to IS, Naji Jerf, was shot dead in Gaziantep in December in a murder that caused international concern.

And at the end of last October, IS claimed responsibility for killing young activist Ibrahim Abdelkader and his friend Fares Hamadi in Turkey.

They were found decapitated in a house in the city of Sanliurfa just east of Gaziantep.