DAMASCUS: Syria rebels overran the Aleppo headquarters of the jihadist Islamic State of Iraq and Greater Syria on Wednesday, as clashes between opposition forces raged into a sixth day.
The loss in Syria's northern second city came a day after ISIS' spokesman threatened to "crush" opposition fighters who have attacked the group in multiple provinces.
Elsewhere, a diplomat announced that two Swedish reporters missing in Syria since November had been freed.
And the fractious Syrian opposition National Coalition said it was postponing until January 17 a final decision on whether to attend peace talks in Switzerland.
On the ground, ISIS battled moderate and Islamist rebels in clashes that erupted on Friday and have killed at least 385 people since then.
Monitoring group the Syrian Observatory for Human Rights announced the new toll in the clashes on Wednesday, saying it included 56 civilians.
ISIS's headquarters in a hospital in the Qadi Askar neighbourhood of Aleppo city was overrun by opposition fighters, who reportedly freed dozens of prisoners held there.
The setback for ISIS came after its spokesman Abu Mohammed al-Adnani issued a defiant message late Tuesday.
He urged ISIS forces to "crush them (the rebels) totally and kill the conspiracy at birth".
"None of you will remain, and we will make of you an example to all those who think of following the same path," he added.
Adnani also warned that ISIS had "declared and begun a war" against the National Coalition and the military command of the opposition Free Syrian Army.
"Everyone who belongs to this entity is a legitimate target for us, in all places, unless he publicly declares his rejection of that group and of fighting the mujahideen (jihadist fighters)."
His message came hours after the head of Al-Qaeda's Syrian affiliate, the Al-Nusra Front, released his own audio message, urging an end to the fighting.
Abu Mohamed al-Jolani warned that the fighting "risks costing us dearly on the ground if it continues".
"The regime will gain new life when it was close to collapse," he added, calling for a ceasefire, exchange of prisoners and the establishment of an Islamic committee to mediate disputes.
He urged all fighters "to give priority to the fight against the regime".
The Nusra Front, Al-Qaeda's official affiliate in Syria, was established in mid-2011 with help from ISIS's Iraqi precursor.
The Iraqi group's chief later sought to merge his group with Al-Nusra, but they rejected the alliance and pledged allegiance directly to Al-Qaeda chief Ayman al-Zawahiri.
Since then, the two groups have functioned separately, though Al-Nusra has remained largely neutral in the latest fighting.
Syrian regime operations continued on Wednesday, with the Observatory reporting at least eight people killed in air raids on the town of Tal Rifaat in Aleppo province.
A security source in Damascus told AFP that the ISIS-rebel fighting benefited the Syrian regime.
"We are the beneficiaries in this situation," he said, describing the fighting as a way for nations backing different rebel groups to "settle scores".
Elsewhere, Sweden's ambassador to Lebanon and Syria confirmed that two journalists missing in Syria since November had been freed.
The two had been named in the Swedish media as Niclas Hammarstroem and Magnus Falkehed.
A spokeswoman for the ICRC in Lebanon said one of the men had been transferred from the Lebanese border town of Arsal to Beirut on Wednesday.
Diplomatic sources said the other was freed on Saturday.
At least 25 journalists have been killed in Syria since the conflict began in March 2011, and more than 30 are thought to be missing.
Both regime supporters and opponents have been accused of abducting and killing journalists.
In Istanbul, a meeting of opposition National Coalition ended without a decision on attending peace talks in the Swiss town of Montreux on January 22.
Amid fierce debate, the coalition's general assembly decided to delay making a decision on opposition participation until January 17, just five days before the conference.
A key Coalition member has said it will boycott the talks, and Damascus has said President Bashar Assad's departure from power will not be up for discussion.