(Adds comment from Tenor, background on Indonesian censorship and apps, byline, SAN FRANCISCO dateline)
JAKARTA/SAN FRANCISCO, 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 animated graphics files, known as GIFs, that are available on the app through third-party services.
WhatsApp said in a statement on Monday that it asked the government instead to work with those providers, which integrate their technology into WhatsApp to allow users to enter keywords to search for GIFs.
Indonesias Internet is partly censored, with access blocked to websites providing criticism of Islam, dating services and sex education, according to research published in May by Tor Project, a nonprofit maker of Web browsing tools.
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 Inc, one of the third parties, said it was attempting to release a "fix." Giphy Inc, another provider, did not respond to requests to comment.
Jennifer Kutz, a Tenor spokesperson, said in a statement that the company is working "to address the content issues raised by the Indonesian government within the next 48 hours."
Kutz said the company "regularly" works with "local entities to make sure our content reflects the cultural mores and legal requirements."
She declined to identify the proposed fix or existing regions with content restrictions. Tenor allows integrators of its service to block potentially objectionable image results or a defined list of search terms.
"In the case of WhatsApp, were taking on this responsibility," Kutz said in an email.
Giphy, a New York City company that also works with WhatsApp, offers its partners a feature for filtering inappropriate images.
Indonesia's warning did not appear to target Gboard, a keyboard app developed by Google that provides comparable GIF search results but must be installed separately from WhatsApp on most devices.
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.
The countrys regulators have reached settlements with several technology companies after threatening to shut them down. In August, Indonesia announced it would block Giphys website for showing gambling-related ads. Access soon was restored after it agreed to cooperate with regulators.
Bans similarly were rescinded in recent years on social media websites such as Vimeo and Tumblr and the chat app Telegram, which regulators had said was "full of radicals and terrorist propaganda."