Gaza's economy will take years to recover from the devastating impact of the war, in which more than 360 factories have been destroyed or badly damaged and thousands of acres of farmland ruined by tanks, shelling and air strikes, according to analysts.

Israeli air strikes on Gaza have resumed since a temporary ceasefire brokedown on Tuesday after rockets were fired from Gaza. The Israeli Defence Force said it launched air stikes on 20 sites on Friday morning and Gaza health officials said two Palestinians were killed in an attack on a farm.

Almost 10% of Gaza's factories have been put out of action, said the Palestinian Federation of Industries. Most other industrial plants have halted production during the conflict, causing losses estimated at more than $70m (£42m), said the union of Palestinian industries. The UN's food and agriculture organisation (FAO) said about 42,000 acres of croplands had sustained substantial direct damage and half of Gaza's poultry stock has been lost due to direct hits or lack of care as access to farmlands along the border with Israel became impossible.

More than 9% of the annual fishing catch was lost between 9 July and 10 August, it added.

"The initial indications are that economic damage caused by the war is three times that of the 2008-9 conflict," said Gaza-based economist Omar Shaban, referring to the Israeli military operation, codenamed Cast Lead. "It's huge."

Unemployment would increase from the prewar rate of 40%, a result of factory destruction, he said. "Recovery will depend on the terms of the ceasefire agreement – whether the siege is lifted, and how quickly. But it will take a minimum of two to three years even if it is lifted."

The ruins of al-Awdah food factory, which was destroyed after days of air strikes and shelling. Photograph: Ibraheem Abu Mustafa/Reuters

Gaza's biggest factory, al Awda in Deir al-Balah, which made biscuits, juice and ice-cream, was destroyed after days of air strikes and shelling last month, which caused a massive fire. Its entire stock of raw ingredients was lost and valuable hi-tech machinery damaged beyond repair. The factory employed 450 people.

"This is a war on our economy," said owner Mohammed al-Telbani. "I started at ground zero, spent 45 years building this business and now it's gone."

Manal Hassan, the factory's manager, estimated the losses at $30m. "We kept a very large stock because of the difficulties of getting raw materials and spare parts into Gaza, so we had enough to keep production going for a year," she said. "This was a factory for making biscuits and ice-cream, not guns. There were no rockets fired in this area."

Dead cow and rotting vegetables at the roadside. Livestock and vegetable farming has been decimated. Photo Sean Smith for the Guardian

At the Nadi family farm in Beit Hanoun, Mahmoud Nadi said almost half the stock of 370 dairy cows had been killed in shelling from tanks positioned inside the border and air strikes. The family, which has farmed in the area for 15 years, fled to UN shelters in Jabaliya when the Israeli ground invasion started.

"When we came back, there were dead cows everywhere. We could hardly reach them because of the smell," he said. The milk yield from the remaining stock had plummeted due to the animals' trauma, he added.

In Beit Lahiya, camel farmer Zaid Hamad Ermelat returned to his land last week to find 20 animals – worth $2,800 a head – had been shot by ground forces. Their decomposing carcasses remained on the ground amid spent bullet casings from M16 rifles.

"This is our only income, supporting 17 members of the family," said the 71-year-old Bedouin, who came to Gaza as a refugee during the 1948 war. Asked what he would do to earn a living, he shrugged he would try to find work as a farm labourer.

Zaid Hamed Ermelat 71 whose camels were killled, and upon which his livelihood depends. Photograph: Sean Smith for the Guardian

In a nearby field, peppers were shrivelled on plants as farmers have been unable to harvest crops during the war.

At a cluster of farms in Juha Deek, nearly a mile from the border, almost every house, store and animal pen was wrecked, fruit and olive trees snapped or uprooted and cattle, sheep and goats killed by shrapnel, bullets or starvation as families fled for safety.

"How do I feel? Look at this," said Ahmed Abu Sayed, 22, gesturing at a view of destroyed buildings and tank-churned land. "This tells you how I feel."

The FAO said it would distribute enough fodder to feed 55,000 sheep and goats for 45 days once a permanent ceasefire had been established.