Authorities in Vietnam arrested a prominent independent journalist Thursday for his criticism of the communist government.

State media reported that Pham Chi Dung was detained by security officers at his home in Ho Chi Minh City and charged with “conducting anti-state propaganda” under Article 117 of Vietnam’s Criminal Code.

According to police, Pham wrote anti-state articles and cooperated with foreign media, to deliver “distorted information.”

The human rights group Defend the Defenders said he contributed to Voice of America and the BBC, under several different pen names.

Pham will be in detention for the next four months as the police investigate, and if convicted could face a sentence of seven to 12 years.

Pham had been arrested once before in 2012 on the same charge but released six months later without being tried. In 2014 he and several other writers founded the Independent Journalists Association of Vietnam (IJAVN), an unregistered entity which “strives to fight for freedom of the press in the Southeast Asian nation,” according to local rights group Defend the Defenders.

Defend the Defenders reported that the journalists association’s website was shut down shortly after the arrest.

Prior to the arrest, he had been frequently harassed by authorities, forbidden to travel overseas in 2014 and under de-facto house arrest since 2013.

Huynh Ngoc Chenh, an IJAVN member, told RFA’s Vietnamese Service Thursday that the arrest showed Hanoi’s desire to exercise greater control over the freedom of speech.

“Pham is the president of IJAVN. He is one of the most active independent journalists. He’s written a lot and is very knowledgeable,” said Huynh.

“His reports are honest and reveal the truth, something the party does not appreciate,” said Huynh, adding, “They want to eliminate his voice.”

According to Defend the Defenders, Hanoi has arrested 29 activists, including 19 bloggers, for writing posts online, and is currently detaining 238 prisoners of conscience.

The country has been consistently rated “not free” in the areas of internet and press freedom by Freedom House, a U.S.-based watchdog group.

Dissent is not tolerated in the communist nation, and authorities routinely use a set of vague provisions in the penal code to detain dozens of writers and bloggers.