Fighters from several Syrian rebel brigades seized the headquarters of the jihadist Islamic State of Iraq and the Levant in the main northern city of Aleppo, an NGO said Wednesday.
"Fighters from several Islamist rebel brigades took control of the children's hospital in the Qadi Askar district, which is the headquarters of the Islamic State of Iraq and the Levant in the city," the Syrian Observatory for Human Rights said.
The Observatory said it was unclear what had happened to "hundreds" of ISIL fighters who had been inside the headquarters.
The rebels freed dozens of people who were being held prisoner in the ISIL headquarters, it added, citing initial reports.
ISIL has been fighting a coalition of moderate and Islamist rebels angered by a spate of abuses by the jihadists, who have been accused of kidnapping and killing civilians and rival rebels.
Late Tuesday, an ISIL spokesman said the group would "crush" opposition fighters and warned that it considered members of the opposition National Coalition and the military command of the Free Syrian Army to be "legitimate targets."
More from GlobalPost: Islamist rebel chief calls for end to infighting in Syria
The political opposition vacillates
Meanwhile, Syria's exiled opposition postponed its decision on whether to take part in UN-hosted peace talks in Switzerland until January 17.
The general assembly of the mainstream opposition National Coalition decided to suspend its debate and meet again in the Turkish commercial hub of Istanbul on January 17, just five days before the peace conference is to take place near Geneva, members said.
"The debates were very heated among the different groups that make up the coalition. It was not possible to take a decision," a source close to the opposition said.
The Syrian National Council, the main component of the coalition, had said Friday it would boycott the conference slated to start in Montreaux on January 22.
The SNC has long said it will not negotiate until President Bashar al-Assad's regime is toppled.
During its last general assembly in November, the coalition said after heated debate that it was ready to take part in the peace conference along with delegates from Assad's regime.
More from GlobalPost: Syrian Islamist rebels fight against Al Qaeda-linked militants
In a statement at the time, the National Coalition, under pressure from Arab and western allies, said it would take part in the peace talks "on the basis of the full transfer of power."
It also stipulated "that Bashar al-Assad and those with the blood of Syrians on their hands have no role in the transitional phase and Syria's future."
However the Syrian government, while expressing willingness to attend the proposed Geneva conference, insists that Assad's departure from power is not up for discussion.
The conference in Montreux is designed to find a political solution to end the civil war in Syria, which has claimed more than 130,000 lives and displaced millions of people since March 2011.