Indonesia's President Joko Widodo has issued a decree allowing authorities to disband organisations deemed threatening to national unity, the country's top security minister said.

The order, signed on Monday and announced on Wednesday, follows months of sectarian tensions and protests in the country, which saw Jakarta's Christian governor Basuki "Ahok" Tjahaja Purnama sentenced to two years in prison for blasphemy against Islam.

It amends an existing law regulating mass organisations and allows the government to sidestep a potentially lengthy court process to implement a ban.

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The decree is "simply aimed at maintaining national unity and the existence of the Indonesian nation," said Wiranto, the coordinating minister for security, legal and political affairs, who goes by one name.

"It's not an act of government arbitrariness or an attack on Islamic mass organisations," he said. 

The decree does not specify which organisations will be disbanded, but the justice ministry has the power to act based on it, the minister said.

New York-based Human Rights Watch condemned the move, calling it a "troubling violation" of the rights to freedom of association and expression despite it being supported by moderate groups such as Nahdlatul Ulama, Indonesia's largest Muslim organisation.

Phelim Kine, the group's deputy Asia director, said the government already has the power to take legal action against any group suspected of violating the law.

"Banning any organisation strictly on ideological grounds is a draconian action that undermines rights of freedom of association and expression," Kine said. 

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If enforced, the decree could ban Islamic group Hizbut Tahrir that campaigns for Indonesia to adopt Islamic law and become a caliphate.

The government announced in May that it planned to ban the group because its activities were not in line with the state's secular ideology and were "causing friction in society". 

The group condemned the newly signed presidential decree and vowed to seek a judicial review in a constitutional court.

"This is tyranny," Ismail Yusanto, a spokesman for the group in Indonesia, said. 

"The move just shows an arbitrary action aimed at disbanding Hizbut Tahrir.

"HTI is a legal religious organisation and has been spreading its messages peacefully, in an orderly manner, in accordance with the law," he said.

Leaders of Hizbut Tahrir Indonesia were among the proponents of last year's massive rallies seeking the prosecution of Jakarta's then governor Ahok, for remarks about the Koran that some Muslims deemed blasphemous.

Purnama - a key ally of Widodo and the first Christian to lead the capital in 50 years - is now serving a two-year jail term after a court found him guilty of blasphemy in May.

Indonesia is the world's most populous Muslim-majority country, but Christians make up about 10 percent of the country's 250 million people. 

Source: News agencies