Abdel Qader Saleh, the charismatic chief of the Syrian rebel Liwa al-Tawhid Brigade, has died of his wounds after a regime air strike last week, rebels and activists said Monday.
His death is a blow to the opposition, particularly in the Aleppo area that Saleh came from and fought in, where the Syrian regime has made a string of advances in recent weeks.
Saleh was considered one of the opposition's most respected commanders, with ties across the opposition seeking to oust President Bashar al-Assad, and his death was widely mourned on Monday.
The 33-year-old "was the first to organise peaceful demonstrations in Aleppo and then the first to attack the bastions of Assad's gangs", the opposition National Coalition said in a statement.
"He became a living symbol in the hearts of the Syrians," the statement added.
Saleh's death was announced by Liwa al-Tawhid on its official Facebook page and confirmed by the Britain-based Syrian Observatory for Human Rights.
"Abdel Qader Saleh, known as Hajji Marea, died of wounds he sustained last Thursday when warplanes targeted the Liwa al-Tawhid leadership," the watchdog 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 Liwa al-Tawhid's intelligence chief Yussef al-Abbas, known as Abu al-Tayyeb.
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 regime informers.
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Saleh, chief of operations for Liwa al-Tawhid, was widely seen as the brigade's most important figure.
A former grain merchant, he was one of tens of thousands of civilians who took up arms as a 2011 peaceful uprising against Assad gradually turned violent.
He was considered a moderate Islamist, particularly compared to the hardline jihadists who have flooded into Syria, and said he sought an Islamic state but with free elections.
"In Europe, all the leaders are Christian because the majority is Christian. In Syria, the majority is Muslim and the government should be too, elected by the people," he told AFP during an interview in March.
Saleh's 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 -- a father of five -- 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, where Saleh was widely known.