Updated

Al Qaeda's North Africa branch claimed Wednesday it is holding hostage a senior U.N. peace envoy, his aide and four tourists kidnapped in the Sahara Desert in recent weeks.

United Nations special envoy for Niger, Robert Fowler, and his aide Louis Guay, both Canadian diplomats, were kidnapped Dec. 14 in the southern Sahara country.

Four tourists, including two Swiss, a German woman and a British man, were kidnapped by gunmen Jan. 22 near the border in neighboring Mali, their tour operator said.

"We announce to the general public that the mujahideen (holy warriors) reserve the right to deal with the six kidnapped according to Islamic Shariah law," the Al Qaeda group said in a statement posted Wednesday on militant Web sites, according to SITE, a U.S.-based organization that monitors militant messages.

The statement's authenticity could not be independently verified, but the Al Qaeda group's purported spokesman, Salah Abu Mohammed, delivered an indentical message to pan-Arab TV station Al-Jazeera hours earlier.

"We are aware of the reports, but we have nothing further to comment," U.N. deputy spokeswoman Marie Okabe said at U.N. headquarters in New York.

The Al Qaeda group did not issue demands for the hostages' release, but in the past it has obtained ransoms for Western tourists kidnapped in the Sahara, the world's largest desert.

"The mujahideen will announce later their conditions in exchange for the release of the kidnapped," Abu Mohammed said in the recording.

Al Qaeda in Islamic North Africa, known by the French language acronym AQMI, is an Algeria-based group that joined Osama bin Laden's terror network in 2006 and conducts dozens of bombings or ambushes each month. It operates mainly in Algeria but is suspected of crossing the country's porous desert borders to spread violence in the rest of northwestern Africa.

AQMI said all six hostages were abducted in Niger and issued the alleged names of the tourists.

The Swiss government said it was aware of the kidnap claims and was actively involved with other European governments in securing the tourists' safety. A British government spokesman said the claim was being analyzed. Germany declined to comment.

No group had previously claimed the tourists' kidnapping. The president of Niger, Mamadou Tandja, has blamed Fowler's abduction on a rebel group from the northern Niger ethnic minority of Tuareg nomads who are battling the government.

Tuareg rebels from the Front For Forces of Redress initially claimed the kidnapping in a statement posted on their Web site, but later retracted that statement, saying its site had been hacked.

Western intelligence officials in Algeria told The Associated Press they believe the U.N. diplomats were initially abducted by local gunmen, bandits or Tuaregs, and later traded to AQMI.

It is not clear who first abducted the tourists, but the intelligence officials believed they are now also being held by AQMI-aligned gunmen who roam the desert along Algeria's southern borders.

Ransom from kidnappings — along with arms, cigarettes and drug trafficking in the Sahara — have become a main source of revenue for AQMI, the intelligence officials said. The officials, who spoke on condition of anonymity because of the nature of their activities, said the cross-border trafficking appeared to be on the rise and was becoming a major regional security concern.

Algerian authorities have not recently commented on the issue. In a rare public count of abductions, Interior Minister Yazid Zerhouni said last year that the country recorded 115 kidnappings "relating to terrorism" or involving demands for ransom in 2007.

Authorities also said this week they had encircled an AQMI unit in the south of the Tebessa region, a zone near Algeria's Sahara where 11 people were killed by roadside bombs in recent days. The state-run APS news agency said security forces killed three militants in the area this week.