JAKARTA (Reuters) - Indonesian authorities have uncovered a group spreading hate speech and fake news online, one of many that they fear could undermine national unity.

A man types on a computer keyboard in Warsaw in this February 28, 2013 illustration file picture. One of the largest ever cyber attacks is slowing global internet services after an organisation blocking "spam" content became a target, with some experts saying the disruption could get worse. REUTERS/Kacper Pempel

Indonesia has an ethnically diverse population of 250 million people, most of them Muslim but with significant minorities from other religions, and unity across the archipelago has been a priority of governments for generations.

Three people were arrested this week on suspicion of being part of a syndicate being paid to spread incendiary material online through social media, police said.

“If this is allowed to continue, it isn’t just about violating the law but also has the potential to damage the unity of this country,” said presidential spokesman Johan Budi.

Budi said it was up to investigators to determine the motive of those behind the campaign, adding police should investigate the issue “right down to its roots”.

National police spokesman Awi Setiyono said the material involved religious and ethnic issues and posts defamatory to government officials.

He declined to comment on the motive, saying investigators were still building their case and had yet to identify who was behind the syndicate, which calls itself Saracen, that has been spreading the material.

The police cyber crime unit said dozens of Facebook and other social media accounts were being sued to spread the material to an estimated 800,000 social media accounts.

Setiyono said investigators had uncovered money transfers of up to $5,000 to pay those spreading the material.

Religious and ethnic tensions flared in the capital, Jakarta, this year when city elections pitted an ethnic Chinese Christian governor, who was accused on insulting Islam, against a Muslim candidate.

Authorities have scrambled to remove hate speech from social media and online forums in an attempt to defuse tension but a growing amount of content encouraging religious intolerance or radicalism is being shared.

Search giant Google said this month it was working with authorities to tackle content deemed to be offensive.