Khan won the 2018 election on an anti-corruption campaign, voted by voters weary of decades of dynastic politics.
Independent analysts say he was brought to power with the support of the military before falling out with the generals.
“Everyone knows who this is. It is the army behind (Khan’s arrest),” 21-year-old PTI supporter Mohsin Khan told AFP outside the party chief’s home.
Cartman said he wanted the military and politicians to “work together”.
The political crisis has been building for months, with Khan attempting to disrupt the coalition government by dissolving the two provincial parliaments he controls and agitating for early elections.
Mobile data services and access to social media platforms including Facebook and YouTube, which were cut off immediately after Khan’s arrest on Tuesday, were partially restored across the country by Saturday.