(Adds social media reaction; paragraphs 12-14)
JAKARTA, Nov 6 (Reuters) - Indonesia on Monday vowed to block Facebook Inc's WhatsApp Messenger within 48 hours if the service did not ensure that obscene Graphics Interchange Format (GIF) images were removed.
WhatsApp, which is widely used in Indonesia, the world's most populous Muslim-majority nation, said message encryption prevented it from monitoring the third-party providers Indonesians use to search for GIFs.
It asked the government to work with the providers instead.
Semuel Pangerapan, a director general at Indonesia's communications and informatics ministry, said WhatsApp would be blocked within 48 hours unless the images supplied by third parties were taken off the service.
"Yes, true. They have to follow the rules of the host," Pangerapan said of the proposed block.
The ministry had sent three letters to WhatsApp over the issue, he said.
"They have responded, but asked us to speak directly to the third party. The GIFs appeared in their apps. Why do we have to be the one speaking to the third party? They are supposed to be the ones managing it," said Pangerapan.
Tenor, a third-party provider of GIFs to WhatsApp, had been blocked, Pangerapan said.
Tenor did not immediately respond to a request for comment.
"In Indonesia, WhatsApp lets people search for GIFs using third-party providers," a Whatsapp representative said in a statement.
"We are not able to monitor GIFs on WhatsApp since content is end-to-end encrypted. We've directed the Indonesia government to work with these third-party providers to review their content."
Indonesia had 69 million monthly active Facebook users as of the first quarter of 2014, ranking the country fourth globally after the United States, India and Brazil, company data showed.
Some reaction on Indonesian social media to the threatened block was sceptical. "While youre at it, why dont you block Twitter too, (and) if necessary all browsers in the Playstore, because its way easier to search for porn there than on WhatsApp, wrote one Twitter user, with the handle zjnessy.
Another, using the handle zyogirswnt, said "Does the government want to block WhatsApp? In the case of Telegram it was only a bluff, but if true, it is so unfortunate."
Indonesia briefly blocked access this year to some channels of the Telegram messaging app, saying its forums were "full of radicals and terrorist propaganda", before reaching a pact with the messaging service on how to rein in propaganda.
The Indonesian Consumers Foundation (YLKI) had urged the communications ministry to block pornographic GIF images accessible via emoticons, complaining that children could easily reach them, according to news website kompas.com. (Reporting by Cindy Silviana; Writing by Ed Davies; Editing by Clarence Fernandez)