Tehran, Iran (CNN) -- Fresh clashes broke out between demonstrators and security forces in Tehran on Sunday as large crowds gathered for Ashura, a major religious observance.
An opposition Web site said three people were killed in the fighting. But, with tight restrictions on international media, CNN could not independently verify the casualties.
The reformist Web site Parlemannews reported that one of the victims Sunday was Saeed Ali Mousavi, nephew of opposition leader Mir Hossein Mousavi.
Tehran Police Chief Azizollah Rajabzadeh denied that any protesters were killed by security forces.
Police did not fire any shots in Tehran, "and security forces were not in possession of firearms," Rajabzadeh told the semi-official news agency ISNA.