Al-Qaeda leader Ayman al-Zawahiri has called in an interview for militants to kidnap Westerners, especially Americans, to exchange them for jihadist captives.

In the second part of an interview with al-Qaeda media arm As-Sahab, which the US-based SITE monitoring service said a jihadist posted on Twitter, Zawahiri was asked what Muslims should do to free militant prisoners.

“I advise them to capture Westerners and especially the Americans as much as they can, to exchange them for their captives,” he replied.

In the first part of the interview, released on April 19, the al-Qaeda chief called for unity amid widening divisions with a rival jihadist organization rooted in the Syrian civil war.

Zawahiri succeeded the late Osama bin Laden as leader of the global terror network in 2011.

On Monday Yemeni officials said 68 al-Qaeda militants were killed in an “unprecedented” US and Yemeni aerial campaign, in a bid to head off attacks by the network’s local affiliate.

Al-Qaeda in the Arabian Peninsula (AQAP) has been linked to a number of failed terror plots against the United States.

A top Yemeni official told AFP the “unprecedented” Saturday-Sunday air war came after “information that al-Qaeda was plotting attacks on vital installations, military and security, as well as foreign interests in Yemen.”