Eyewitnesses say Iraqi police have surrounded the People’s Mujahideen of Iran (PMOI) camp and clashes are continuing inside.
Iran wants the camp closed. The exiles fear they will be forcibly repatriated.
The US gave the camp some protection until it handed security control back to Iraq earlier this year.
The PMOI said Iraqi riot police stormed the camp using batons and live fire on Tuesday.
Amnesty International said it was “seriously concerned” about the incident, and had seen footage which “clearly showed” Iraqi forces beating people repeatedly.
There are contradictory reports coming out of Ashraf about what sparked the violence.
Police say residents of the camp fired teargas at them but the PMOI says it was the police who fired the tear gas.
An Iraqi official told AFP news agency more than 50 Iranians had been arrested.
Iraqi officials said they were trying to establish a police post in the camp, north of Baghdad. “It is our territory and our right to enter, to impose Iraqi law on everybody,” a defence ministry spokesman told al-Arabiya television.