Opposition rallies in Iran have frequently turned violent
Iranian authorities have warned opposition supporters against using text and e-mail messages to organise protest rallies.
The country's police chief said these systems were monitored and people misusing them would be prosecuted.
Gen Ismail Ahmadi Moghaddam also said opposition supporters should not think internet proxies would protect them.
Following post-election protests, the government blocked several pro-reform websites and stopped text messages.
Without newspapers, Iran's young opposition supporters have constantly turned to the internet and mobile phone to communicate with each other and the outside world, organising demonstrations and distributing images and news of violence against them.
Iran's head of police said disseminating the opposition's plans deserved great punishment.
"These people should know where they are sending the SMS and e-mail as these systems are under control. They should not think using proxies will prevent their identification," Mr Ahmadi Moghaddam said.
He warned that those who incited others to protest or issued appeals: "have committed a worse crime than those who come to the streets".