Rights activists, journalists and lawyers around the world have been targeted with phone malware sold to authoritarian governments by an Israeli surveillance firm, media reports say.

They are on a list of up to 50,000 phone numbers of people believed to be of interest to clients of the company, NSO, leaked to major news outlets.

It is not clear where the list came from - or whose phones had actually been hacked.

NSO denies any wrongdoing.

It says the software is intended for use against criminals and terrorists and is made available only to military, law enforcement and intelligence agencies from countries with good human rights records.

In a statement, it said the original investigation which led to the reports, by Paris-based NGO Forbidden Stories and the human rights group Amnesty International, was "full of wrong assumptions and uncorroborated theories".