Microsoft has launched an “urgent” external inquiry into allegations Israel’s military surveillance agency has used the company’s technology to facilitate the mass surveillance of Palestinians.

The company said on Friday the formal review was in response to a Guardian investigation that revealed how the Unit 8200 spy agency has relied on Microsoft’s Azure cloud platform to store a vast collection of everyday Palestinian mobile phone calls.

The joint investigation with the Israeli-Palestinian publication +972 Magazine and the Hebrew-language outlet Local Call found Unit 8200 made use of a customised and segregated area within Azure to store recordings of millions of calls made daily in Gaza and the West Bank.