Defeated Iranian presidential candidate Mir Hossein Mousavi says arrests cannot halt the pro-reform movement. (Vahid Salemi/Associated Press)

Anti-government protests will continue in Iran, despite reports that pro-reform lawyers and other activists are being arrested, the country's opposition leader said Monday.

"The pro-reform path will continue," Mirhossein Mousavi said in a statement, according to Reuters. "The establishment should respect the constitution and let us to gather to commemorate our killed loved ones on Thursday."

Mousavi, along with another opposition politician, Mehdi Karoubi, have called on the government to allow demonstrators to gather in a Tehran square Thursday to remember the victims of recent anti-government violence.

Since Iran's disputed June 12 presidential vote, hundreds of thousands of Iranians have held protests denouncing the election as fraudulent until security forces launched a heavy crackdown, arresting hundreds and killing at least 20, according to police. Rights groups believe the number could be far greater.

Activist groups allege government forces are continuing to arrest prominent human rights lawyers in an attempt to spread fear.

Mousavi said such arrests would not thwart the pro-reform movement, said the Reuters report.

"The killings and arrests are a catastrophe, people will not forgive those behind such crimes," Mousavi said, adding: "I am sure the judiciary is not informed about many arrests."

"The country of 70 million cannot become a prison for all of them. The more they arrest people, the bigger this movement becomes."

Details several cases

International rights group Human Rights Watch detailed several cases of arrests of lawyers in Iran and said others have been threatened and told not to talk to media — especially foreign outlets.

According to the report, Iranian police officers snatched prominent lawyer Shadi Sadr from a Tehran street on Friday as she walked to prayers. A friend who was with her at the time said she was beaten with a cable and thrown in a car that sped away, said the report.

At least four other Iranian human rights defenders — Mohammad Ali Dadkhah, Abdolfattah Soltani, Mohammad Mosatafaie, and Kambiz Noroozi — have been arrested, according to HRW. Mostafaie was later released but the others remain in custody.

The New York-based group released the statement on the clampdown Sunday, a day after global protests backed by HRW and Amnesty International that urged Iran to end the crackdown on opposition activists and release those detained.

Protests have also been held the world over in sympathy with the Iranian pro-opposition supporters, and Saturday saw rallies in 80 cities, including in the United States.

The protesters demanded Iran release hundreds, or even thousands, of people detained during protests denouncing hardline President Mahmoud Ahmadinejad's return to power.

With files from The Associated Press