An Amnesty board member has been arrested by Indonesian police after a video of him singing a protest song critical of the country’s military was circulated online.

Robertus Robet, a human rights activist and sociology professor at Jakarta’s State University, was arrested late on Wednesday evening for alleged criminal defamation.

The well-known activist is being charged under Indonesia’s controversial electronic information and transactions law, which is increasingly being used to prosecute and silence government critics.

Robertus Robet. Photograph: Andreas Harsono

Robet was arrested in relation to a song delivered at an event called Kamisan, a weekly human rights demonstration held in front of the state palace in Jakarta every Thursday.

The national police spokesman Dedi Prasetyo said on Thursday that Robet is being investigated for hate speech and faces up to two years in prison if convicted.

At the event on 28 February, Robet sang a song that was popular among student protestors in 1998, when massive demonstrations led to the fall of authoritarian dictator Suharto, who ruled Indonesia for more than three decades.

Robet’s song was meant as a criticism of the government’s recent plan to move unemployed military generals into civil institutions to address an institutional surplus.

The move has sparked anger and concern within Indonesian civil society about creeping authoritarianism in the world’s third-largest democracy, and criticism that some policies of president Joko Widodo’s government are reminiscent of Suharto’s New Order era.

Prominent human rights figures have condemned the arrest.

Human rights researcher Andreas Harsono told the Guardian that Robet’s arrest would have “a chilling effect on free speech in Indonesia”.

The Indonesian branch of Amnesty International described Robet’s detention as “a threat to freedom of expression and opinion, and a threat to human rights defenders in Indonesia”.

“This arrest does not only show violations of the right to freedom of expression and opinion, but also proves that the New Order-style silencing practices still occur,” Amnesty’s Papang Hidayat, told kompas.com.