Major Iranian cities were gripped overnight by new mass rallies denouncing the Islamic republic, as the son of the ousted shah urged protesters on Saturday to plan to seize city centres.

The two weeks of protests have posed one of the biggest challenges to the theocratic authorities who have ruled Iran since the 1979 Islamic revolution, although supreme leader Ayatollah Ali Khamenei has expressed defiance and blamed the United States.

Following the movement’s largest protests yet on Thursday, new demonstrations took place late on Friday, according to images verified by Agence France-Presse and other videos published on social media.

This was despite an internet shutdown imposed by authorities, with monitor Netblocks saying early on Saturday that “metrics show the nationwide internet blackout remains in place at 36 hours”.

In Tehran’s Saadatabad district, people banged pots and chanted anti-government slogans including “death to Khamenei” as cars honked in support, a video verified by Agence France-Presse showed.