Indonesia's Communications and Information Ministry has told Internet service providers (ISPs) in the country to block access to Web messenger Telegram as it has been found to be used by terrorists.

"There are many channels on their service that contain radicalism propaganda, terrorism, hatred, provocation, instructions to assemble bombs, strategies to attack, disturbing images and other contents that are against the Indonesia law," said the ministry in a statement issued yesterday.

The statement from the ministry, however, did not indicate when the eight ISPs in Indonesia must comply with the request to block Telegram.

Also, if implemented by all eight ISPs, the block would affect Telegram's service only on desktop computers.

People can still use the smartphone app version of the service, which is used more widely.

The ministry, however, said it was preparing to shut down the Telegram app "comprehensively in Indonesia if Telegram does not prepare a Standard Operating Procedure (SOP) to deal with unlawful contents on their application".

Telegram has more than 100 million users, according to the number of downloads from the Internet.

It is said to be a non-profit cloud-based instant messaging service that also provides optional end-to-end-encrypted messaging.

Telkomsel - one of the eight ISPs in Indonesia - has said it will adhere to the move. The rest have yet to respond.

It has been widely reported that Telegram has been used by militant groups to communicate in Indonesia and elsewhere around the world, including the Islamic State of Iraq and Syria (ISIS).

Santoso, one of the country's most-wanted terrorists until he was killed last year, used Telegram to communicate with his men from the ISIS-affiliated East Indonesia Mujahideen, or Mujahideen Indonesia Timur.

Correction Note: This story has been updated to correct a quote from Indonesia's Communications and Information Ministry.