Chinese officials have closed a leading neo-Maoist website for a month because it posted sensitive political content, according to its founders.
At least one other leftist site was also suspended.
The move comes amid the country's most serious political crisis in two decades, after the dismissal of Chongqing party secretary Bo Xilai, who promoted "red culture" and was championed by the Utopia website. Debates between left and right are heating up ahead of this autumn's transition of power to a new generation of leaders.
Utopia was closed for a few days immediately after Bo's sacking last month, reopening after articles about Chongqing were removed.
A notice posted on Friday said three government agencies had ordered it to close for a month while it underwent self-examination because it had "published articles that violated the constitution, maliciously attacked state leaders and speculated wildly about the 18th Party Congress". The congress will officially select the new leaders.
The announcement added that the officials from the State Council Information Office, the Beijing internet management office, and the Beijing police internet security office had warned that the site could only go back online with their approval.
"Our staff asked for a list of articles that they thought violated the constitution and said we would certainly co-operate and deal with these problems. They did not have any specific articles or evidence. In the end, the conversation was cut short and rudely ended," it said.
The notice was later replaced with a message saying the site was under maintenance.
Fan Jinggang, the general manager of Utopia, said the closure came two and a half hours after he posted the announcement at midday on Friday.
"I think it is because of both tighter control of the internet and also the nature of Utopia as a left[wing] platform," he said.
The site is staunchly opposed to the economic reforms that liberals have pressed in recent months and Fan recently told the Economist that attacks on Bo were the work of "anti-China forces".
A volunteer at the office for the Maoflag website, which was available a few days ago but closed on Friday, said he had learned of its closure that morning.
"It's the government's action. We have to obey. When they say we should stop, then I'll stop. After all, I'm just a volunteer," he said, declining to give his name.
Asked when the website might become available again, he replied: "Heaven knows."
Other closed sites included Mao's Time, iMaoZedong and Mao Zedong's Art.
