Hundreds of journalists in Iran have received an anonymous text message warning against contact with "hostile" organisations outside the country, the ISNA news agency reported.

"All contact and collaboration with hostile elements based abroad, by mail or other methods of communication, is a crime and will be brought to justice. This SMS is the last warning," the message said.

Iranian media reported that as many as 700 journalists and public figures received the SMS on Friday evening.

Lawmaker Ali Motahari said the message had "created worry among journalists."

"The intelligence ministry cyber-police must find the origin of this SMS and inform the public, and the judiciary must act against those responsible," he said.

"The Press Supervisory Board is responsible for the media and other bodies must not interfere."

Some journalists who received the message said on social media that they would lodge complaints.

Iran bans its citizens from having any contact with Persian-language media based overseas, including the BBC's Persian service and Voice of America.

In April, an Iranian court sentenced four journalists arrested in November 2015 to between five and 10 years in prison for "colluding" with foreign governments and harming "national security".

The journalists, some of whom work for reformist media outlets, were part of a group arrested by the elite Revolutionary Guard, which accused them of being "members of a network of infiltrators linked to Western governments" it said were hostile to the Islamic republic.

Iran last month accused a British-Iranian woman, an employee of the Thomson Reuters Foundation which supports journalists around the world, of seeking to overthrow the government.

Nazanin Zaghari-Ratcliffe was accused of being "involved in the soft overthrow of the Islamic republic through... her membership in foreign companies and institutions," the Mizan news agency, which is close to the judiciary, reported.

Freedom House in April ranked Iran among the 10 least free countries in the world. Satellite dishes are illegal and Persian-language broadcasts from outside the country are often jammed, it said.