Several thousand people converged on the guarded neighbourhood containing the US consulate in Pakistan's port city of Karachi Friday, dpa reported.
Television footage showed demonstrators pushing defensive shipping containers aside, while at least one police officer was seen being removed on a stretcher.
In Lahore, several hundred demonstrators threw stones at riot police, who responded with tear gas. Similar protests were also occurring in other towns, including Rawalpindi and Peshawar.