The Red Cross reported on Monday that one of its local teams had managed to restore water supplies to 40 per cent of the 1.2 million population of Basra, which has been severely bombarded by US and UK forces.
Care International said there was "a slight sense of relief" that power and water supplies had not so far been hit by the bombing of Baghdad.
It has launched a new appeal for funds to support its 30-strong team in Iraq.
The British Overseas Aid Group has also called on the Government to donate more funds to the international humanitarian relief operation. It says the contribution so far is tiny in relation to the £1.75 billion given to the armed forces.
"We are deeply concerned about the serious effects of war on an Iraqi population already suffering an acute humanitarian crisis and largely dependent on food aid," says a new statement from BOAG, which comprises Oxfam, Cafod, Christian Aid, ActionAid and Save the Children.
Clare Short, the international development secretary, has announced an extra £10 million for aid work in Iraq, mainly through UN programmes.
This comes in addition to £8 million the department is spending on Iraq in 2002-3.
The main humanitarian work is being co-ordinated by the UN, which has set up a 'humanitarian hub' in Cyprus. Inside Iraq, 3,500 UN staff continue to administer the 'oil for food' programme which feeds 16 million of the 27 million Iraqi population.
British Aid agencies, often working with the UN or other partners, are trying to anticipate and respond to humanitarian needs as the war develops.
The Red Cross, which has also launched an appeal for funds, has ten delegates and 100 local staff in Iraq who will focus on helping wounded and internally displaced people, expected to total tens of thousands.
Care International, which has a UK division, specialises in providing clean water in Iraq and has 30 Iraqi staff in its Baghdad office. Its main concern is that war damage to electricity supplies will halt the pumping of water and sewage.
Oxfam is working with Unicef and the UNHCR in Syria, Jordan and Iran to prepare water supplies for refugees. It is supplying water and sanitation kits which contain emergency pumps and storage tanks.
CAFOD is helping its partner Caritas Iraq to convert its 14 'well baby' clinics into first-aid centres. Staff have had training from doctors experienced in war wounds and the clinic has been given ambulances and supplies.
Medecins Sans Frontieres, which has a UK branch, has kept a team of six international staff in Iraq. Their job is to assess medical needs as the war develops and determine what the best response would be.
Save the Children is active in Jordan, Turkey, Kuwait, Iran and northern Iraq. It is planning to provide medical supplies and health care in refugee camps, special feeding programmes, tents and plastic sheeting. Other aims are protecting children from exploitation and reuniting them with their families.
Christian Aid's work in Iraq is mostly in the autonomous Kurdish area of the north. In recent days it has been working to respond to the developing situation with various partners including the Middle East Council of Churches.
ActionAid sent an assessment team to Iraq two weeks ago but decided that it couldn't add to the work of existing agencies. It is chair of the British Overseas Aid Group and is coordinating media and advocacy responses to the Iraq crisis.