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.

Yussef 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.

The brigade's top commander, Abdelkader Saleh, and another senior figure of the group, Abdelaziz Salameh, were wounded.

Following the attack, Liwa al-Tawhid arrested 30 people accusing them 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 around 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. The Observatory says, however, that fighting is still underway.

The group also reported heavy fighting on the main highway linking Homs to the capital Damascus, in the strategic Qalamun mountain range that spreads to Lebanon where regime forces can rely on allies from the Shiite movement Hezbollah for support.

Government troops also raided the Wadi al-Mawla village in the Homs countryside on Friday, the Observatory said, adding that two soldiers and nine men were killed in the attack.

The Observatory, which relies on medics and activists for its information, said that according to unconfirmed reports a number of women were also killed when the army entered the village.

The opposition Syrian Revolution General Commission, meanwhile, spoke of a "massacre" in Wadi al-Mawla in which "entire families" were killed and homes set on fire.

The report could not be independently verified.

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.