A blast rocked a primary school in Libya’s restive second city Benghazi during playtime on Wednesday, wounding six children, security and medical officials said.

The blast was caused by an explosive device thrown over the exterior wall of the school as the children were playing, said Fadia al-Barghathi, spokeswoman for Benghazi’s Al-Jala hospital.

Benghazi, the cradle of the 2011 NATO-backed uprising that toppled Moamer Kadhafi, has seen near-daily attacks on security and other targets in recent months as the weak central government has tried to rein in former rebel brigades turned militias.