Tehran's reformist mayor was replaced yesterday following claims he was threatened with arrest if he did not step down.

Mohammad Ali Najafi, who took power after reformists swept the council elections last May, said he was suffering from unspecified health problems that required extensive treatment. But his allies say he was under pressure after accusing his conservative predecessors of corruption.

Morteza Alviri, a member of the council and a former mayor, said on Sunday that Najafi was summoned one night to the prosecutor's office. "I'm informed he was summoned, not in a polite manner", Alviri said in a video posted on the reformist Khabaronline website. He said Najafi was woken while in bed. "I heard he was threatened with arrest," Alviri added.

Najafi had attracted criticism from hardliners last month after attending a show at City Hall for Iranian Women's Day in which schoolgirls performed a traditional dance.

Islamic law in Iran prohibits public dancing, and prosecutor general Mohammad Jafar Montazeri said the show included "acts against public morality" and Islamic tradition. Najafi resigned a few days later, citing health reasons he had not previously mentioned. The council rejected his decision, prompting the prosecutor general to accuse them of playing "a political game" and calling on Najafi to submit a fresh resignation, which he did on Monday.

The second resignation was approved by the council yesterday, and he has been temporarily replaced by a deputy, Samiollah Hosseini Makarm.

Najafi's supporters strongly criticized the prosecutor's involvement, and asked why he was not instead focused on the corruption allegations revealed by the mayor. Reformists displaced the conservatives for the first time in 14 years in last year's municipal elections.