TEHRAN: The main prayer service in the Iranian capital has been interrupted by repeated chants of "Death to America" — despite this week's landmark nuclear deal with world powers that was welcomed by authorities in Tehran.

The chanting by several hundred hard-liners came as conservative cleric Mohammad Ali Movahedi Kermani was leading the Friday prayers at the Tehran University campus.

He praised Iranian nuclear negotiators for their efforts in concluding the nuclear deal and criticized the United States for its tough sanctions on Iran.

Anti-US chants are frequent at gatherings of hard-liners in Iran.

Since the deal was reached earlier this week with world powers led by the US, Iranian hard-liners have offered mostly mild criticism while scores of ordinary Iranians have welcomed the agreement with street celebrations.