The body of Zainab was found on Tuesday in a garbage bin, police officer Omran Nawaz Khan said. Authorities said she was kidnapped, raped and killed.
This horrific crime has provoked widespread popular anger in Pakistan. Activists on social media have condemned the government for failing to arrest those involved in the crime.
Violence broke out Wednesday in the city of Kasur, hours before the funeral of the girl Zainab.
Angry citizens attacked a police station and a nearby government building in Punjab province, sparking clashes that killed at least two people and wounded several others.
"The police are trying to contain the violence and find those involved in the killing and arrest of the girl," said Rana Thanaullah, the provincial justice minister.
Shopkeepers closed their stores in Kasur on Wednesday, expressing anger at the killing of the girl.
For her part, Pakistani activist Malala Yusuf expressed her deep sorrow over the fate of the girl Zainab, wrote Malala on her account on Twitter: "My heart was on Zainab, a 7-year-old girl raped and killed violently in Kasur, Pakistan, this must stop the government The concerned authorities must take steps. "