JAKARTA (Reuters) - Indonesian police arrested an Amnesty activist for insulting the military, the group said on Thursday, after he compared a plan to allow senior officers to hold civilian positions to the days of autocratic leader Suharto.

Robertus Robet, a board member of Amnesty International Indonesia, was arrested late on Wednesday, the group said in a statement.

Asked about details of the arrest, police spokesman Dedi Prasetyo cited a law under which those who intentionally insult a public institution face jail of up to 18 months.

Prasetyo did not give further details.

Police arrested Robet based on a speech made during a rally last week in which he spoke against a plan by the government to allow senior military officers to hold civilian positions in government institutions, Amnesty said.

The plan “brought to mind the Indonesian Armed Forces (ABRI) dual function in New Order era”, Amnesty said, referring to the military under Suharto rule.

A video circulating online also showed Robet singing during his speech.

“The song was intended as my criticism of the ABRI of the past not the Indonesian National Military (TNI) of the present, let alone intended to insult the profession and institutional organization of the TNI,” Robet said in a televised statement on Thursday.

Amnesty said in a statement Robet’s arrest was “not only a clear threat to the freedom of speech and expression in Indonesia, but also poses a threat for human rights activists in general”.

Suharto, who ruled Indonesia with an iron fist for 32 years, was forced from office in 1998 as the world’s fourth most populous nation descended into economic and social chaos.

Much of the blame for that crisis focused on the nepotism and corruption that became the hallmark of Suharto’s later years in power and which saw family members and close associates amass fortunes and come to dominate Indonesia’s economy.