The new head of the Islamist group Ahrar al-Sham, once one of the strongest militias in the Syrian civil war, has urged fellow insurgents to fight on after a blast on Tuesday wiped out its senior leadership.

In a video on YouTube, Ahrar al-Sham said Hashem al-Sheikh, also known as “Abu Jaber”, had been named its new leader and Abu Saleh Tahan its new military chief. Another video showed a man identified as Abu Jaber exhorting his men to fight on. The explosion in northwestern Syria killed at least 12 including Ahrar al-Sham’s former leader Hassan Aboud, said the group which is part of the Islamic Front alliance fighting both the Syrian army and the now dominant Islamic State movement.

Reports have it that, the blast killed 28 of Ahrar al-Sham’s commanders, dealing a major blow to the organization that is believed to have received funds from Gulf states.

 Abu Jaber said on the video while eulogizing the dead that, “Jihadi men of our nation … do not let the crisis shake you or the calamity divide you… “Rise, let us die for what they have died for.”

Some 50 of the group’s leaders had gathered at a house when the blast went off inside. There has been no claim of responsibility for the blast, which took place in Syria’s Idlib province.