Fighters linked to al-Qaida abducted a Spanish journalist and a photographer in a rebel-held Syrian province in September, their families said on Tuesday.

Journalist Javier Espinosa and photographer Ricardo Garcia-Vilanova were taken by rebel group the Islamic State in Iraq and the Levant (ISIL) on 16 September at a checkpoint in Raqqa province, which fell to militant Islamist brigades in March, the journalists' families said.

Espinosa, who works for El Mundo newspaper, and freelance photographer Garcia-Vilanova were a few kilometres from the border with Turkey and were trying to leave Syria at the time. They were taken to Raqqa city. They were travelling with members of the rebel Free Syrian Army, who were also taken by ISIL but released after 12 days.

The incident had not been reported until now because of negotiations with the rebels holding the men.

"We have reached an impasse with the captors after many weeks of attempted mediation," Monica Preito, Espinosa's wife and fellow journalist who has covered the Syrian civil war, said at a news conference in Beirut.

"Today we appeal to the Syrian people and all armed groups to help release Javier and Ricardo who have always been committed to show the human face and suffering of the Syrian people during these very difficult times," she said.

The pair are veteran journalists who have covered the Syrian conflict since its beginning and have travelled to the region around 10 times.

Fifty-five journalists have been killed and 30 are still missing in Syria, according to the New York-based Committee to Protect Journalists, making it the most dangerous place in the world for media workers.

Syria's conflict began with peaceful protests in March 2011 and developed into an armed insurrection when these were violently suppressed. More than 100,000 people have been killed and fighting has broadly settled into a stalemate.

Hardline Islamist groups have exploited the power vacuum in many rebel-held areas to exercise their authority at the expense of more moderate opposition factions.