The country has a history of those in power using the police and courts to stifle their political opponents, and Prime Minister Sharif has several pending cases brought against him while in opposition.
One senior PTI official, Shahbaz Gill, has been in detention for nearly two weeks after being arrested following a TV interview in which he urged army officers to disobey orders that went against the interests of the country.
Khan said Gill had been tortured and sexually abused in custody, and vowed action against those responsible.
“That includes the inspector general, deputy inspector general of police and a magistrate who sent him on physical remand despite knowing he was tortured,” he said.
Khan said the government had turned the country into a “banana republic”.
“There is no law here and any charges can be brought against anyone,” he said.
Khan’s main goal is an early general election – the next one must be held before October next year – but the government has shown no sign of wanting to go to the polls.
“I think if an election is not called soon, Imran Khan’s popularity will further grow so he shouldn’t be concerned,” said Talat Masood, a former general and now political analyst.
“These massive demonstrations show that Imran Khan has the backing of millions of supporters, but this also shows that the public lacks interest in parliamentary democracy,” he said.
Khan swept into power in 2018 thanks to an electorate weary of the dynastic politics of the country’s two major parties, promising to sweep away decades of entrenched corruption and cronyism.
But under his rule the country’s economy went backwards, and the IMF suspended the loan programme that the new government has only just gotten back on track.
Khan also lost the support of the powerful military.
Still, analyst Masood said he doubted the former prime minister would be jailed on any of the charges he faces.
“The courts might fine him, but going harder will be counterproductive,” he said.