Ahrar al-Sham, a Syrian armed opposition organisation, has announced its new leadership after it lost its top brass during a bomb attack on a high-level meeting in Idlib province.
Hassan Abboud, the head of Ahrar al-Sham, was among up to 45 people killed in an underground bunker near an ammunition dump outside Ram Hamdan on Tuesday.
The new head is Hashim al-Sheikh, also known as Abu Jaber, while his deputy is Abu Saleh Tahan, the group announced on Wednesday.
It pledged to keep fighting against Syrian government forces and the Islamic State armed group, Reuters news agency said.
Along with Abboud, about 50 of the group's leaders had been gathered at a house when the blast went off, according to the Syrian Observatory for Human Rights, a group that monitors the conflict.
There has been no claim of responsibility for the blast.
It is not known who staged the attack but Islamic State sympathisers hailed the death of Abboud on social media.
Another of Ahrar's leaders, Abu Khaled al-Souri, a close associate with al-Qaeda leaders Osama bin Laden and Ayman al-Zawahiri, was killed by the Islamic State earlier this year.
That assassination caused the schism that pitted the Islamic State against other rebel factions in Syria.
Ahrar has about 20,000 fighters and is the main force in the Islamic Front alliance, which was formed earlier this year to oppose the Islamic State group besides battling the forces of President Bashar al-Assad.
Ahrar advocates for a state run on Islamic principles, which protects the rights of women and religious and ethnic minorities, and disagrees with the approach of the Islamic State group.