TEHRAN, Iran — Violence and acrimony over Iran's disputed election intensified Sunday, with word that the authorities had detained more than 100 prominent opposition members, riots erupting in Tehran and other cities, and the incumbent hinting that his top challenger could face punishment for calling the result a sham.

Two of the three opposition candidates and a clerical group issued fresh statements requesting annulment of the Friday election that gave a lopsided victory to the incumbent, Mahmoud Ahmadinejad, a conservative who has become a polarizing figure at home and abroad. They did so despite a decree from Iran's supreme leader, Ayatollah Ali Khamenei, that the outcome was fair.

It was unclear how far Ahmadinejad's adversaries were willing or able to go in challenging the result. But supporters of the opposition candidates skirmished with baton-wielding riot police officers on the edges of a government-organized victory rally in Tehran. There were also reports of riots in other Iranian cities, and the protests were echoed by Iranians demonstrating against the election results in Washington and in several European capitals.

Ahmadinejad dismissed the opposition's allegations of fraud, saying that the victory had given him a bigger mandate than ever. He criticized Mir Hussein Moussavi, the main opposition candidate — who remained at home on Sunday with security forces closely monitoring his movements — in a veiledstatement that many here saw as a threat.