Popular pornography websites XVideos, Redtube and Pornhub have been blocked by two ISPs in the Philippines.
Customers of Smart and Sun Cellular said they could no longer access the sites on portable devices or desktop computers.
Instead, users see a message saying the sites have been blocked because of anti-child-pornography laws.
The Philippines government has not given any official explanation of why the sites have suddenly been blocked.
However, the country's National Telecommunications Commission confirmed to CNN that it had ordered all the nation's ISPs to block access from 14 January,
But social media chatter suggests customers using Globe and other ISPs can still access the sites.
Pornhub recently reported visitors in the Philippines spent the longest average time on its site.
The average viewing time in the Philippines was 12 minutes and 45 seconds, said Pornhub - about three minutes longer than the global average.