TEHRAN – Iranian protesters attacked police stations late into the night onMonday, news agency and social media reports said, as security forcesstruggled to contain the boldest challenge to the clerical leadership sinceunrest in 2009.

Videos on social media showed an intense clash in the central town ofQahderijan between security forces and protesters who were trying to occupya police station, which was partially set ablaze.

There were unconfirmed reports of several casualties among demonstrators.

In the western city of Kermanshah, protesters set fire to a traffic policepost, but no one was hurt in the incident, Mehr news agency said.

Demonstrations continued for a fifth day. Some 13 people were reportedkilled on Sunday in the worst wave of unrest since crowds took to thestreets in 2009 to condemn the re-election of then-president MahmoudAhmadinejad.