Ayman al-Zawahiri
Ayman al-ZawahiriSite Intelligence Group

Al-Qaeda leader Ayman al-Zawahiri has called on Muslims to kidnap westerners to use as bargaining chips in negotiating the release of jailed Islamist militants.

In a wide-ranging interview, the figurehead of the terrorist organisation also offered support for the Muslim Brotherhood, which was ousted from power in Egypt following a military coup. Zawahiri also urged Islamist groups in the Syrian civil war to join forces in defeating president Bashar al-Assad.

Zawahiri called for the release of Egyptian cleric Dr Omar Abdel Rahman, who was jailed for his role in the 1993 bombing of New York's World Trade Centre.

"I ask Allah the Glorious to help us set free Dr Omar Abdel-Rahman and the rest of the captive Muslims, and I ask Allah to help us capture from among the Americans and the westerners to enable us to exchange them for our captives," said Zawahiri, according to the Site website monitoring service, after the video was posted on radical Islamist website Hanein.

Reuters reported that though the recording was not verified as authentic, the voice matched that of al Zawahiri.

The Egyptian-born doctor urged Islamist groups in Syria, including the Islamic State of Iraq and al-Sham (ISIS), to cease fighting with one another, and to depose "the criminal al-Assad regime."

"The Ummah [Muslim world] must support this jihad with all that it can, and the mujahideen [Islamist militants] must unite around the word of Tawhid [unity]," said Zawahiri.

"So everyone should prioritise the interest of Islam and the Ummah over his organisational or partisan interest, even if he gives up for his brothers what he sees as right."

In February, al-Qaeda broke from ISIS over the group's refusal to break of its operations in Syria and concentrate on Iraq. In Syria, al-Quaeda has allied itself with the al-Nusra front.

When asked about Egypt, al-Zawahiri declared: "The duty on every Muslim is to deter the aggressor by any means, and especially the oppressed Muslims."

He said the deposed Islamist group the Muslim Brotherhood had "all the right to use force against the injustice they are facing."

"The secularists and the army attacked them with Gulf money, American planning, Israeli incitement and crusader plotting," he added.

Last year, the Egyptian army ousted elected president Mohamed Morsi and arrested him alongside hundreds of his Islamic Brotherhood supporters. They declared the Islamist group a terrorist organisation last year.

In the first part of the recording, released last week, al-Zawahiri said that al-Qaeda was far from defeated, and was in fact expanding, more than a decade after President George W Bush launched the 'war on terror' following the 9/11 terrorist attacks.

"The upper hand is for the one who does not withdraw from his land," he said. "Who has withdrawn from Iraq, and who has not? Who has withdrawn from Afghanistan and who has not?"