In earlier years, Pinterest, used mainly to share photos, had occasionally faced access issues from China but those seem to have become permanent since the middle of last week, GreatFire said.
The blockade coincides with the celebration -- from March 5 to 15 -- of the annual session of China's legislature, the biggest annual political event of the Communist government, during which censorship and pressure against human rights activists are stepped up, Efe news reported.
Efe news also verified that the photo sharing site could not be accessed from computers in Beijing or Shanghai on Friday.
Pinterest was one of the few social media sites still accessible on Chinese territory, where Twitter, Facebook, Instagram, Tumblr, Google Plus, Snapchat, Line and Telegram have been blocked for some time now.
Other websites censored in China include the Google search engine and the video sharing website YouTube, although many netizens in the country find ways to access the blocked sites.
Pinterest President Tim Kendall had said last year that the site "isn't a social network" but a "catalogue of ideas" which according to him, explained why it was still allowed in China.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)