The partner of journalist Glenn Greenwald, who reported on National Security Agency leaker Edward Snowden’s disclosures of secret surveillance programs, was detained at London’s Heathrow Airport by security.

The Guardian reported that David Miranda, who lives with Greenwald in Brazil, was held by officers for nearly nine hours and told he was being questioned under a U.K. anti-terrorism law. 

He was released without charges, but authorities confiscated electronic equipment, including his cellphone, laptop, camera and memory sticks.

Greenwald called the detainment of Miranda “a profound attack on press freedoms and the news gathering process.”

"To detain my partner for a full nine hours while denying him a lawyer, and then seize large amounts of his possessions, is clearly intended to send a message of intimidation to those of us who have been reporting on the NSA and GCHQ [U.K.  Government Communications Headquarters]. The actions of the U.K. pose a serious threat to journalists everywhere,” he said.

“But the last thing it will do is intimidate or deter us in any way from doing our job as journalists. Quite the contrary: It will only embolden us more to continue to report aggressively,” Greenwald added.

Miranda had been traveling from Berlin to Rio de Janeiro, passing through London. In Berlin he had met with Laura Poitras, a documentary filmmaker who has worked with Snowden.

Snowden, a former government contractor, disclosed classified documents revealing the NSA’s surveillance of phone and Internet traffic. He is wanted in the U.S. on espionage charges but has found refuge in Russia, which granted him temporary asylum.

WikiLeaks, which has been aiding Snowden, criticized Miranda’s treatment in a tweet on Sunday. “We denounce the UK authorities abuse of terrorism legislation to detain NSA journalist Glenn Greenwald's partner. Brazil must act,” the group said. 

Greenwald last month said there were more disclosures coming from Snowden. 

“There are vast programs of both domestic and international spying that the world will be shocked to learn about, that the NSA is engaged in with no democratic accountability and that’s what driving our reporting,” Greenwald said.