Syrian security forces are keeping up a fierce assault on dissent as the embattled regime faces surprising calls for an end to the violence from its strongest ally, Iran.

Activists said there were reports of machine-gun fire and explosions as military vehicles stormed an area near the Turkish border Thursday.

President Bashar Assad's crackdown on the 6-month-old uprising has left the regime increasingly isolated.

Late on Wednesday, Syrian ally Iran joined the international chorus of criticism.

Iranian President Mahmoud Ahmadinejad said Assad should back away from his violent crackdown and talk to the opposition.

Ahmadinejad's comments to Portugal's Radiotelevisao Portuguesa, were broadcast with a simultaneous Portuguese translation.