The conflict in Gaza has caused serious damage to crops, herds and fishing as well as greenhouses and irrigation systems, bringing food production to a halt and sending prices sharply higher, the United Nations food body said on Thursday.

The Rome-based Food and Agriculture Organisation (FAO) said in a statement that virtually the entire local population of about 1.8 million was dependent on food aid and significant long term help would be needed for local farms to recover.

Ciro Fiorillo, head of FAO's office in the West Bank and Gaza Strip, said specialists had been able to make a series of field visits to the coastal Palestinian enclave to prepare a detailed assessment of the damage during the latest ceasefire.

He said bomb damage, water and electricity shortages and financial problems, as well as the uncertainty about a possible resumption of military activities had caused major problems.

"Under the most recent ceasefire many farmers and herders are now able to access their lands, however resumption of food production faces serious obstacles", he said.

Food prices have shot up for many items since the start of hostilities, with egg prices up 40 per cent, potatoes up 42 per cent and tomatoes up as much as 179 per cent.

FAO said there had been substantial direct damage to the 17,000 hectares of croplands in Gaza and the area had lost around half its population of poultry either through direct hits on shelters or by lack of feed or water.

Around 64,000 sheep and goats needed feed and water, while the fishing sector had lost 234.6 tonnes of potential catch in from July 9 to August 10, around 9.3 per cent of the annual catch.

According to FAO, some 19,000 people in Gaza rely on farming for their livelihoods, with a further 6,000 living from livestock raising and another 3,600 dependent on fishing.

It said it could begin distributing fodder to sheep and goats as well as 4,000 water tanks as soon as a permanent ceasefire was established.

Israel and Hamas militants, who control Gaza, extended a three-day truce on Wednesday by a further five days to give Egyptian mediators more time to try to secure a peace deal.

Israeli forces launched an offensive against the Gaza Strip on July 8 with the declared aim of halting rocket fire out of the territory. It later sent in its ground forces to destroy a large network of infiltration tunnels.

It pulled its troops out of Gaza last week, but efforts to agree to a permanent ceasefire have so far failed. - Reuters