Tens of thousands joined protests in Pakistan's capital on August 17 led by opposition figure Imran Khan and cleric Tahir ul-Qadri, demanding Prime Minister Nawaz Sharif step down.
The protests have raised concerns about Pakistan's stability barely a year after Sharif took power in a landslide election win that marked the first democratic transfer of power in the country's history.
Khan, a former international cricket star, claims the May 2013 elections that Sharif won were rigged.
Qadri and Khan arrived in Islamabad late on August 15 after a two-day procession through Punjab province.
Late on August 16, Qadri said, "We are giving 48 hours for the government to resign and dissolve the assemblies and present themselves before the law."
Qadri demands Sharif's arrest over what he alleged was the murder of his supporters.