A huge blast Wednesday at a Hamas military base in southern Gaza lightly injured more than a dozen people, including children, Hamas officials said. It appeared the explosion was accidental.

Hamas did not say what caused the blast in a crowded neighborhood in the town of Rafah and the Israeli military said it wasn't involved. Israeli warplanes often target Hamas weapons facilities, but Israel usually confirms those attacks.

The Gaza-based Palestinian Center for Human Rights has repeatedly called on Hamas not to store explosive materials in civilian areas. It said a similar explosion in August wounded 58 people and destroyed seven houses.

Explosives stored by Palestinian militants often explode prematurely or detonate while bomb makers are working with them.

Hamas said five children, three women and five other people were all slightly injured by flying glass from the explosion.

Hamas, an Iranian-backed militant group, has controlled Gaza since expelling forces loyal to Palestinian President Mahmoud Abbas in a violent takeover in June 2007. Abbas now controls the West Bank, leaving the Palestinians with rival governments in the two territories they claim for a future state.

In the West Bank on Wednesday, Palestinians said Jewish settlers set fire to a girls school near the northern city of Nablus. The school was found vandalized with Hebrew graffiti on the wall reading "regards from the hills." Jewish settlers live on hilly outposts nearby.

The Israeli military said a complaint had been received from Palestinians and Israeli police were investigating. The fire caused minor damage.

The incident appears to be the latest action in a campaign extremist Jewish settlers call the "price tag." They say it is their response to moves by the Israeli government to remove unauthorized settlements or restrict settlement construction.

Two weeks ago, arsonists torched a West Bank mosque, scrawling "revenge" on a wall in Hebrew and charring copies of the Muslim holy book.

The West Bank government is conducting talks with Israel in hopes of reaching a peace agreement establishing an independent Palestinian state. To advance that goal, Abbas' prime minister, Salam Fayyad, has launched an ambitious economic development plan to prepare the way for independence.

The Palestinian transportation minister said Wednesday that his ministry has finished designing an airport in the West Bank. Sadi Kruns said construction on the $340 million project — a centerpiece of the Palestinian development plan — should get under way by the middle of next year.

"We rely on the international community, particularly the U.S. and European Union ... to provide the required funds and to remove the obstacles that might emerge," he said.

Israeli Foreign Ministry spokesman Yigal Palmor was dismissive. He said the Palestinians were apparently not interested in talking to Israel.

"It sounds absurd to built an airport unilaterally if you don't have proper agreements on airspace control, which they don't have," he said.