Foreign Affairs Minister Lawrence Cannon is calling in the top Iranian diplomat in Canada over the arrest of a Canadian journalist in Tehran.

"Minister Cannon is calling in the Iranian charge d'affaires to express our grave concern about the arrest of a Canadian journalist and about the general situation," said Andre Lemay.

He said Canadian consular officials in Tehran are sending a diplomatic note to Iranian authorities to demand immediate access to Maziar Bahari, an Iranian-Canadian who was detained Sunday while working for Newsweek magazine.

The charge is the highest-ranking Iranian diplomat in Ottawa. Neither country has had an ambassador in the other's capital for a about a year in a diplomatic skirmish over acceptable candidates. The charge runs the embassy in the absence of an ambassador.

Prime Minister Stephen Harper also criticized Iranian authorities in a statement Monday.

"The reaction of the Iranian authorities to the demonstrations in Iran is wholly unacceptable," he said.

"The regime has chosen to use brute force and intimidation in responding to peaceful opposition regarding legitimate and serious allegations of electoral fraud."

Harper called on Iran to release political prisoners and journalists who have been unjustly detained and allow free reporting on events there.

Bahari, an Iranian-Canadian, was detained while working for Newsweek magazine.

Online profiles of Bahari say he was born in Iran in 1967 and studied in Montreal, where he earned a degree in communications from Concordia University.

Newsweek says he is a Canadian citizen who has been living in and covering Iran for the last decade.

The magazine has called for his immediate release and is asking western governments to use their influence on his behalf.

Bahari is one of at least two dozen journalists and bloggers arrested in Iran since protests began there a week ago over the recent presidential election.