Ismail Haniyeh noted that Gaza had still not recovered from the destruction previously suffered in a three-week war with Israel in December 2008 to January 2009.
Mr Haniyeh said: "We urge Arab brothers and the international community to stand beside the Palestinian people and Gaza in order that we can reconstruct what has been destroyed by the [Israeli] occupation and to rehabilitate the infrastructure."
Donor states pledged some £3 billion for Gaza reconstruction in 2009 but little of that promised aid has materialised, apart from £250 million guaranteed by the wealthy Gulf emirate of Qatar just weeks before the outbreak of the latest conflict.
Israel and Mr Haniyeh's ruling Islamist movement Hamas, which governs the Gaza Strip, agreed to an Egyptian-drafted ceasefire two weeks ago to end eight days of fighting.
Israel launched its air offensive last month with the stated aim of stopping Gaza militants from firing rockets at its southern towns and cities.
About 170 Palestinians, more than half of them civilians, died in the fighting.
Six Israelis were killed, four of them civilians.
Estimates vary of the extent of property damage and business losses in Gaza, a small, widely impoverished coastal enclave of around 1.7 million Palestinians.
A Hamas administration spokesman put direct losses at £338m. Counting indirect losses the total was about £435m, he added.
The spokesman said 200 residential buildings and dozens of government offices were destroyed.
Omar Shaban, a prominent Gaza economist, has estimated that the direct losses from destroyed buildings, security compounds and infrastructure at around £156m, in addition to £15m in indirect losses arising from the suspension of production in factories and businesses.
Mr Shaban expected that Qatar would be among the first to offer aid.
The Israeli government has issued no figures on economic losses during the conflict, which disrupted life mainly in the south of the country and led to the mobilisation of some 40,000 military reserve troops.
The Israeli financial daily Globes newspaper, citing figures from economists and business groups, estimated the loss of production at 0.2% of gross domestic product, or two billion shekels (£322m).
Direct damage from Palestinian rocket fire that hit homes, cars and factories was about 25 million shekels (£4m), the business information firm BDI said.
Israel's Finance Ministry has said it plans to compensate those who suffered damage and for lost wages in the south.