Some 200 Palestinians gathered in Martyrs Square late Tuesday and set fire to tires, demonstrating against a decision ending exemptions for camp residents from electricity costs, the Palestinian news agency Ma'an said Wednesday.
Protesters threw stones and glass bottles. More than 20 officers were injured, Red Crescent officials said.
Jibrin al-Bakri, the city's governor, said while he supports peaceful protests anyone who destroys or damages property will be held accountable.
An agreement signed by Palestinian Prime Minister Salam Fayyad earlier in the week changed the status for refugee camp residents, who had been exempt from paying for electricity, the Palestinian news agency said.
Mahmud Ishtayeh, a Fatah official in Nablus, called on the North Electric Co. to delay handing out fines to camp residents who refuse to pay their bills until an agreement is reached with the Palestinian Authority government.