China has a history of tightening its censorship of internet services during times of political upheaval, and that's unfortunately happening again with massive pro-democracy protests underway in Hong Kong. Both monitoring sites and on-the-ground observers report that the country has blocked access to Instagram on the mainland, most likely to prevent images of the demonstrations from spreading beyond Hong Kong (where Instagram is still working). It's potentially a big blow to free speech, as the photo sharing service was one of the few foreign social networks that operated unfettered in the area. We've reached out to Instagram for more details, but it's safe to presume that China won't lift its restrictions so long as the protests continue -- and it won't be surprising if this ultimately proves to be a permanent ban.

[Image credit: Alex Ogle/AFP/Getty Images]