“Are they no longer cracking down on pornographic websites? A lot of porn sites and forums are accessible,” one blogger wrote.
Chinese surfers have long been accustomed to government Internet blockades. The country has been cracking down on pornographic websites and blocking them, but various porn sites remain accessible.
Still unanswered are questions about whether it's an official change in policy, a technical glitch or some sort of test by the usually disapproving Chinese Internet police.
Websites about human rights and dissidents are also routinely banned.
"Maybe they are thinking that if Internet users have some porn to look at, then they won't pay so much attention to political matters," an Internet analyst said.
The Chinese government has the most extensive Internet policing system, from technical filters that block sites based on certain words to human monitors who scan bulletin boards and micro-blogging posts.
Few Chinese will admit to surfing for porn because it is illegal. Many sites are still inaccessible. Sites that somehow evade control are usually blocked within hours. But the demand is there.
"The more they restrict something, the more people pay attention," said a 29-year-old, who surfs for porn on business trips.
Though various well-known Chinese-language sites remain blocked, those that suddenly became available around late May include the English-language site YouPorn and PornHub, along with numerous Chinese sites offering downloads.
The government has not said why the sites were unblocked.