At least one police officer and three protesters were killed in clashes between the far-Right Islamist party Tehreek-e-Labbaik Pakistan (TLP) and security personnel.
The TLP had called for a march from Lahore to Islamabad to protest against Israel over the war on Gaza, ahead of US President Donald Trump's announcement of a ceasefire deal.
The TLP's often violent street protests have troubled multiple Pakistani governments.
The march started on Friday, with TLP members vowing to stage a pro-Palestinian demonstration outside the US embassy.
Author's summary: Violent clashes erupt in Lahore during anti-Israel protest.