Three organizations in Britain have filed a lawsuit at the European Court of Human Rights, accusing their country's eavesdropping agency of using its online surveillance programs to violate the privacy of millions of citizens.

English PEN, Big Brother Watch and the Open Rights Group claim that Britain's Government Communications Headquarters, known as GCHQ, acted illegally by collecting vast amounts of data, including the contents of emails and social media messages.

The legal challenge came after documents disclosed by U.S. National Security Agency leaker Edward Snowden exposed the extent of mass data gathering carried out by NSA and GCHQ.

Lawyer Daniel Carey said Thursday that papers for the lawsuit were filed this week at the court, which is based in Strasbourg, France.

GCHQ did not immediately return calls seeking its comment.