A fighter from the Tawhid Brigade, which operates under the Free Syrian Army, fires an anti-tank missile in Aleppo, November 14, 2013. REUTERS/Molhem Barakat (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) Image Credit: REUTERS

Beirut: A Syrian air strike has killed a senior commander of the Islamist Liwa Al Tawhid rebel brigade in Aleppo and wounded its chief and another leader, a watchdog said Friday.

Four more rebel chiefs were killed in other incidents, three in the northern Aleppo province and the fourth in Homs to its south, the Syrian Observatory for Human Rights said.

Youssuf Al Abbas, known as Abu Al Tayyeb, was intelligence chief for Liwa Al Tawhid and was killed in a strike Thursday on an army base captured by the rebels a year ago, the Britain-based Observatory said.

He had been in a car along with the brigade’s top commander, Abdul Kader Saleh, and another senior figure of the group, Abdul Aziz Salameh, both of whom were wounded.

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

The powerful brigade is among a number of Islamist units that have rejected the mainstream opposition Syrian National Coalition.

Meanwhile, two chiefs of rebel battalions were killed in fighting with loyalist forces near the international airport outside Aleppo.

A security source in Damascus confirmed that there were still rebel pockets of resistance in the environs of the airport.

Elsewhere in the province, a former army colonel who commanded another rebel brigade was killed in fighting in the Maarat Al Artiq area.

For three weeks, the army has been pressing a campaign to retake rebel-held areas in Aleppo, particularly east of the country’s second city, and jihadist fighters have called for mass mobilisation to counter regime advances.

Syria expert Fabrice Balanche told AFP the regime is aiming to progressively fragment rebel territory in the north of the country.

“The army is trying to cut off eastern parts of Aleppo held by rebels from [their bases] in the countryside,” he said.

“At the same time, it is trying to open an approach to Idlib and Jisr Al Shughur [both southwest of Aleppo] to break up rebel territory, taking it bit by bit.”

Meanwhile, in Homs province, to the south of Aleppo, a rebel chief was killed in Mahine, which the army said it had captured, along with a large cache of arms there that had been seized by the insurgents.

However, the Britain-based Observatory said fighting was still underway there.

An estimated 120,000 people have been killed and millions displaced by Syria’s civil war, which erupted after a fierce government crackdown on pro-democracy protests first held in March 2011.