Iranian police have arrested several people campaigning for a reformist candidate in this month’s presidential election, an aide said Sunday, as a senior official pledged to impose ideological limitations on the race.

Police picked up several supporters of candidate Hasan Rowhani after he delivered a speech Saturday night, his campaign manager, Mohammad Reza Nematzadeh, told the semiofficial Mehr news agency.

“Some people were detained on the street after leaving the meeting,” he said.

The June 14 election is to choose a replacement for President Mahmoud Ahmadinejad, who cannot run for a third term. Authorities have already pared down the list of candidates to eight, disqualifying Ahmadinejad’s top aide and a former president who could have galvanized opposition to the harsh clerical system.

That was a clear indication that Iran’s rulers did not want an open contest that could end up in a disputed outcome of the type that set off widespread riots when Ahmadinejad was re-elected in 2009.

On Sunday, after the arrests, a top official warned that Rowhani and others would be limited in their election drive.

“Police will confront individuals who have counter-revolutionary behavior” during campaigning, said the Iranian police chief, Gen. Ismail Moghadam, according to the police website. “It is natural that police have carried out their tasks.”

An exile-based Iranian opposition website reported that authorities arrested at least seven people who attended Rowhani’s campaign appearance.

It said the arrests were made after participants chanted slogans calling for the release of Mir Hossein Mousavi, an opposition leader and candidate in the disputed 2009 election, who has been under house arrest for more than two years.

A council of advisers to influential former reformist President Mohammad Khatami has urged Rowhani to unite with the other major reform-leaning candidate, Mohamed Reza Aref.

A statement on Khatami’s personal website expressed hope that the two could form a “united front” to field a single nominee.

Nematzadeh said the two candidates have not met to discuss the possibility.

Aref’s star has been rising since his performance in a Friday debate of the eight candidates, restoring some energy to the reform movement after their main candidate, former President Akbar Hashemi Rafsanjani, was disqualified.

Also Sunday, four aides to another candidate, Saeed Jalili, were injured in a road accident. Jalili, Iran’s chief nuclear negotiator, is considered a front-runner in the campaign. The accident happened on the way to the city of Ghazvin, about 70 miles west of Tehran. Jalili was in a different vehicle and was not hurt.

Iran is among the world’s leaders in the number of road accidents per capita. More than 20,000 people are killed on the roads there every year.