PARIS, France (AFP) — 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 (US).

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

This was despite an internet shutdown imposed by the authorities, with monitor Netblocks saying early 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 AFP showed.

Other images disseminated on social media and by Persian-language television channels based outside Iran showed similar large protests elsewhere in the capital, as well as in the eastern city of Mashhad, Tabriz in the north and the holy city of Qom.

In the western city of Hamedan, a man was shown waving a shah-era Iranian flag featuring the lion and the sun amid fires and people dancing.

In the Pounak district of northern Iran, people were shown dancing round a fire in the middle of a highway, while in the Vakilabad district of Mashhad, people marched down an avenue chanting “death to Khamenei.” It was not possible to immediately verify the videos.

Reza Pahlavi, the US-based son of Iran’s ousted shah, hailed the “magnificent” turnout on Friday and urged Iranians to stage more targeted protests this Saturday and Sunday.