BEIRUT: The head of the Syrian rebel Liwa al-Tawhid Brigade has died of wounds suffered in a regime air strike last week, rebels and a monitor said on Monday.

“Abdel Qader Saleh has been martyred,” said a posting on a Facebook page linked to the brigade.

The Britain-based Syrian Observatory for Human Rights also reported the death.

“Abdel Qader Saleh, known as Hajji Marea, died of wounds he sustained last Thursday when warplanes targeted the Liwa al-Tawhid leadership,” it said in a statement.

“He was taken to Turkey after being wounded, and died in a hospital there before being brought back to Syria for burial,” Observatory director Rami Abdel Rahman told AFP.

Thursday's strike also killed Yussef al-Abbas, known as Abu al-Tayyeb, Liwa al-Tawhid's intelligence chief.

He had been in a car along with Saleh, and another senior figure in the rebel group, Abdelaziz Salameh, who was also wounded.

Following the attack, Liwa al-Tawhid arrested 30 people suspected of being informers for the regime of President Bashar al-Assad.

Saleh, chief of operations for Liwa al-Tawhid, was widely seen as the brigade's most important figure.

His death comes as the Syrian regime makes new gains in Aleppo, seizing several towns and talking about reopening Aleppo International Airport after nearly a year of closure.

“As an individual, he was very, very important certainly in the Aleppo area, but increasingly, as an individual that many in Syria felt represented the revolution,” said Charles Lister, an analyst at IHS Jane's Terrorism and Insurgency Centre.

“He came from a humble background, was outwardly religious but was very open — and he maintained extremely good relations with almost all groups of all different natures.”Lister said Saleh's death would be “a very significant blow” to the opposition, but added that it could “spur on the rebels to launch a counterattack as the regime advances”.

In a sign of his good ties across the opposition spectrum, Saleh was being widely mourned on social media sites by activists and fighters from a range of groups.

Liwa al-Tawhid, which is backed in part by Qatar, has some 8,000 fighters and is among a number of Islamist units that have rejected the mainstream opposition National Coalition.

It does participate in the military command linked to the Coalition, and is one of the best known rebel brigades fighting in the Aleppo area, and Saleh was widely known in the region.