Congressional leaders have been urged by the largest American-Muslim rights group to probe US military contractors following reports of them continuing to spy on Muslims using data gathered from religious apps.

The Council on American-Islamic Relations (CAIR) said on Monday it wrote to the US House and Senate committees on judiciary, armed services, and intelligence after WSJ reported that Google banned apps targeting Muslims with data-harvesting software.

The software was developed by a company tied to US national security contractors.

"CAIR is urging Congress to protect American Muslims, in addition to Muslims overseas, whose Islamic prayer apps and their corresponding cellphone data continue to be spied on by multiple US military contractors - and purchased by the US military," said Robert McCaw, government affairs director at CAIR.

"This ongoing spying on American Muslims' cellphone metadata and Islamic app usage is a direct attack on the First Amendment rights of our community and its consumer privacy."

In its letter to US lawmakers, CAIR said that Muslim Americans have had to endure spying, profiling, and other forms of government discrimination thanks to these apps, and stressed that a full and public congressional investigation is needed to explore this documented case of the US military purchasing the movement and location data of millions of Muslim app users.