Algeria on Thursday expressed "deep concern" following press reports that it may have been the target of the Israeli-made Pegasus spyware as it launched a probe.

The foreign ministry denounced what it termed an  "inadmissible, systematic attack on human rights and fundamental freedoms" and singled out neighbouring Morocco for "spying on Algerian officials and citizens".

Morocco and Algeria have repeatedly sparred over the disputed region of Western Sahara, which Morocco considers an integral part of its territory while Algeria backs the pro-independence Polisario movement.

Relations between the two neighbours soured again on Sunday after Algeria recalled its ambassador in Morocco for consultations after Morocco's envoy to the United Nations expressed support for self-determination for Algeria's restless Kabylie region.

News outlets, including Le Monde and the Washington Post, had reported on Sunday that the software, developed by Israeli firm NSO Group, had been used by governments to spy on activists, journalists, lawyers and politicians around the world.

The bombshell claims were based on a document leaked to Forbidden Stories, a Paris-based media nonprofit, and Amnesty International.

It contained 50,000 telephone numbers of people identified as potential targets via Pegasus between 2016 and June 2021. 

Many numbers on the list were clustered in 10 countries including Morocco.

Morocco said on Monday it "categorically rejects" claims its intelligence services used Pegasus to monitor critics at home and abroad.

It also filed a defamation claim against Amnesty International and the French NGO, due to allegations its intelligence services used Pegasus against dozens of French journalists.