DUBAI (Reuters) – Al Qaeda’s wing in North Africa published photographs on the Internet on Thursday of four of six Western hostages it says it has in its custody.

Earlier this week al Qaeda in the Islamic Maghreb claimed in an audio tape aired on Arabic broadcaster Al Jazeera that it had a Canadian U.N. envoy and his aide and four Western tourists who were kidnapped in the West African Sahara in December.

A posting on Islamist websites on Thursday showed three separate images of what it said were a Swiss couple, a German woman and a British man, surrounded by men bearing rifles.

In the photographs the women’s faces have been blurred.

An accompanying statement reiterated comments by a spokesman in the audio tape saying they “reserved the right to deal with the six captives under Islamic sharia (law)” — an apparent threat they might be killed if demands are not met — and would issue conditions soon for the release of the hostages.

Niger’s President Mamadou Tandja said last month investigations indicated “terrorists” had kidnapped Canadian U.N. envoy Robert Fowler and his aide Louis Guay who went missing in the country in December.

A senior Malian military source involved in investigating the kidnapping of the four tourists in northern Mali said the al Qaeda-linked group was most likely to be holding them.

Malian officials initially blamed Tuareg rebels for abducting the two Swiss nationals, one German and one Briton near Mali’s border with Niger in January.

Al Qaeda in the Islamic Maghreb, formerly known as the Salafist Group for Preaching and Combat (GSPC), has claimed a series of attacks in the region in recent years, including the kidnapping last year of two Austrian tourists abducted in Tunisia who were later freed in Mali.