In separate statements, the two leaders called on Iran to abide by international obligations to respect the rights of the Iranian people to demonstrate for political change.

Iran's Supreme National Security Council said eight people were killed in the latest series of clashes over the weekend, making the unrest the deadliest since June.

The latest fighting came on the anniversary of Ashura, a major Shiite Muslim holy day marking the death of Imam Hussein, grandson of Prophet Mohammed, as a martyr. Large crowds pour into streets each year for the observance.

Merkel's statement said she condemned the latest clashes "where the unacceptable behavior of the security forces has led to the deaths of people."

Both the United States and Germany have been part of negotiations intended to prevent Iran from developing nuclear weapons.