Eleven Iranians accused of sending insulting SMS text messages about Islamic republic founder Ayatollah Ruhollah Khomeini have been arrested in the southern province of Shiraz, a newspaper reported on Monday.
"After monitoring social network applications on mobile phones like WhatsApp, Viber, Line and tango ... 11 people were arrested," the provincial Revolutionary Guards chief, General Esmail Mohebipour, said.
"They recognised the error of their ways," the Haft e-Sobh daily cited the general as saying.
On Saturday, Iran's judiciary issued a one-month ultimatum for the government to ban such social networking apps, in a move that would boost existing restrictions on Internet use.
The ultimatum came after the discovery of messages criticising Khomeini.
Local media reports said similar messages had also been sent about current officials in the Iranian government, including supreme leader Ayatollah Ali Khamenei.
Iran has a policy of filtering online content, which leaves popular websites such as Facebook, Twitter and YouTube inaccessible without the use of illegal software.
Internet censorship is a bone of contention between conservative hardliners and government members including President Hassan Rouhani who use social networks.
Official figures show that more than 30 million Iranians also use such applications.
Rouhani has said that Internet censorship is counter-productive, and one study showed that 69 percent of young Iranians use special software to get round the restrictions.
In May, the president vetoed a plan to ban WhatsApp after it was bought by Facebook founder and CEO Mark Zuckerberg.
In Iran, Zuckerberg has been dubbed the "Zionist manager" of Facebook because of his Jewish heritage.