Mr Ahmadinejad urged students to fight liberal teachers

He told a group of students that they should organise campaigns to demand that the liberal teachers be sacked.

Mr Ahmadinejad said it was difficult to alter secular influences that had been in place in Iran for 150 years, but added that such a change had begun.

The move echoes campaigns of the 1980s, when hundreds of liberal university teachers and students were sacked.

"A student must yell against liberal thoughts and the liberal economy," the AFP news agency reported Mr Ahmadinejad as saying.

"A student must ask why a secular teacher gives low marks to a student that does not have the same ideas as him."

Last year, an ayatollah was appointed to run Tehran University, sparking protests by students.

Earlier this year, dozens of liberal professors and teachers were retired.

But the BBC's Frances Harrison in Tehran says many have found new jobs with institutions run by people linked to the president's political opponents.