At least 13 Palestinians were killed and dozens injured early Wednesday when Israeli artillery fire hit a school used as a shelter by displaced people in the northern Gaza Strip town of Jabaliya, medical sources said.

Health ministry spokesman in Gaza Ashraf al-Qedra said that hospitals in the northern Gaza Strip have so far received the bodies of 13 killed people and dozens of injured civilians who sheltered at a United Nations-run school in Jabaliya town.

Al-Qedra said in previous statements that 20 people were killed.

Israel has not commented on the incident so far.

On July 25, Israeli army struck a UN-run shelter school in the northern Gaza Strip town of Biet Hanoun, killing 16 displaced people and injuring more than 100 others.

The Israeli military offensive on the Gaza Strip, which was launched on July 8 to end Palestinian rocket firing into Israel, has claimed the lives of 1253 Palestinians and 56 Israelis, including 53 soldiers.

Regional and international efforts to end the ongoing fighting between Israel and Palestinian factions in Gaza have been going on unabated.