After six days of Israeli bombardment, aid agencies say that Gazans are facing a humanitarian crisis with air strikes causing severe problems in getting food, medicine and fuel supplies to the besieged civilian population.

The assessment, by several international relief organisations, contradicts the statement by the Israeli Foreign Minister, Tzipi Livni, during a visit to Paris yesterday that "there is no humanitarian crisis in the Strip, and therefore there is no need for a humanitarian truce". While relief shipments were allowed into Gaza by the Israeli authorities in the days before the start of the offensive, they came after weeks of virtually no supplies getting through, the agencies point out.

The biggest difficulty is that many people are too frightened by bombing to venture out to collect food rations. Gaza officials are also unwilling to take part in food distribution because they could be considered legitimate targets by the Israeli military for working for the Hamas-run administration. Chris Gunness of the United Nations Relief and Works Agency, which looks after 750,000 refugees in Gaza, said: "How can one carry out proper relief work in these conditions of violence? The people of Gaza have already suffered the most stringent economic sanctions. There are obviously problems with giving out aid. Even when people want to get food for their hungry family, they are very aware of the dangers they are facing in going out."

Mr Gunness said the agency carried out food distribution yesterday. "But, as things stand now, we have only a few days supply left."

Doctors inside Gaza report that hospitals are running out of medicine and equipment as the toll of dead and injured continues to rise and puts further pressure on stretched resources. Anaesthetics, antibiotics and drugs for cancer and other long-term illnesses are in short supply along with syringes and IV fluids.

Dr Hassan Khalaf, of the main Shifa hospital in Gaza City, said that Palestinian civilians are paying a terrible price: "We are getting really badly injured people coming in every day. What is the point of saying you are allowing food in for people when you then go on to bomb them? The Israelis may say they are just attacking Hamas but I am seeing children and women coming covered in blood. What we are seeing is a war on the people. The Hamas fighters firing the rockets are at the border, they are not in the city.

"We have organised the hospitals so that different ones are looking after different types of injuries. But the common problem we face is that we are having bad shortages in lots of things, especially anesthetics and antibiotics. We are talking to the ICRC [International Committee of the Red Cross] and I hope we shall get some help."

A serious shortage of industrial fuel is also exacerbating the difficulties for civilians after Israeli forces stopped supplies because the crossing points into Gaza were coming under regular rocket attacks, creating the danger of conflagrations. At the same time, the destruction of tunnels between Gaza and Egypt has blocked alternative routes for procuring transport diesel used by Palestinian households.

Christine Van Nieuwenhuyse, head of the World Food Programme for Gaza and the West Bank, acknowledged that a "significant amount" of food was allowed in by the Israelis before the start of the air strikes. "But we must not forget this came after weeks when hardly any food had got in at all. One of our warehouses is full but we have another one empty as it is in an area which has seen a lot of bombings.

"Our partners in Gaza are the Ministry of Social Welfare and their officials are not taking part in the distribution process because they feel they might get bombed for working for a Hamas government. This is a serious problem as is the fact that people are finding it difficult to move about. We are facing an acute food crisis."

Maxwell Gaylard, the UN's humanitarian co-ordinator for Gaza and the Palestinian territories, said "Gaza is facing a serious emergency, that is a fact. Food supplies have been allowed in but there are huge problems caused by the lack of industrial fuel and this is causing severe problems. To address all these problems we need a ceasefire."

Mark Regev, spokesman for the Israeli Prime Minister said "We are doing our utmost to avoid unnecessary suffering for civilians. What we cannot understand is the claim by officials from the ministries there that they cannot take part in the relief effort because they will be targeted. This is nonsense, perhaps the real reason is that it is in the interest of Hamas to ensure that food does not get to the people due to their own particular agenda."