Catholic Online Forum

Chinese internet users who are skilled at evading the country's online blocks have suddenly found they are again being denied access to some websites.

In China, if you want access to forbidden websites including Facebook or Twitter, one of the easiest ways is to use a virtual private network (VPN).

But in recent days VPNs across China have been either inaccessible or swiftly shut down.

Service providers have blamed the outage on an update to the so-called Great Firewall, which the Chinese government uses to control internet access.

They say the upgraded firewall appears to have the ability to discover and block attempts to circumvent online censorship.

In addition, an army of censors keeps a close eye on the country's weibos - Twitter-like microblogs inside the firewall that have been used to organise protests and challenge official accounts of events, such as a deadly 2011 rail crash that sparked fierce criticism of the government.

Posts on contentious issues are rapidly deleted and sometimes those using banned terms, which can at times even include senior leaders' own names, are blocked entirely.