Iranian protesters on Thursday stepped up their challenge to the clerical leadership with the biggest protests yet of nearly two weeks of rallies, as authorities cut internet access and the death toll from a crackdown mounted.

The movement, which originated with a shutdown on the Tehran bazaar on Dec. 28 after the rial currency plunged to record lows, has spread nationwide and is now being marked by larger-scale demonstrations, including in the capital.

The protests have troubled the authorities under supreme leader Ayatollah Ali Khamenei, already battling an economic crisis after years of sanctions and recovering from the June war against Israel.