"My paramount concerns are for the safety and protection of civilians, the provision of adequate resources to the civilian population, and guaranteed access and security for humanitarian workers," the UN High Commissioner for Human Rights, Sergio Vieira de Mello, said in a statement.
"Fundamental human rights norms must be respected at all times," he added. "No one shall be arbitrarily deprived of his or her life. No one shall be arbitrarily detained and no one shall be subject to torture. Every person shall be presumed innocent. There must be no attacks on civilians and the sick and wounded must be cared for."
Warning that Iraqi children are "extremely vulnerable," with more than one million under the age of five malnourished, the UN Children's Fund (UNICEF) urged all parties to abide by their international humanitarian obligations.
"I urge them to do all in their power to protect children's lives, their health, and their general well-being," UNICEF Executive Director Carol Bellamy said in a statement.
For his part, UN refugee agency chief Ruud Lubbers urged Iraq's neighbouring countries to keep their borders open to those in need of temporary protection and assistance.
"Despite all of the UN's efforts to find a peaceful solution, we are now faced with the sad reality of war in Iraq and more suffering for the Iraqi people," Mr. Lubbers, UN High Commissioner for Refugees (UNHCR), said in a press statement. "We must do everything we can to alleviate that suffering, including keeping borders open so that those fearing for their lives can reach safety in neighbouring states."
UNHCR has recently intensified its efforts to help Iran and Jordan prepare for a possible refugee influx. According to the agency's chief of mission in Iran, Philippe Lavanchy, the situation at the Iran-Iraq border crossings was calm on Thursday morning, with no reports of Iraqi refugee movements into Iran following the start of strikes on Iraq.
"Our preparations for a possible influx of refugees has been severely hampered by lack of funding by donors, who had been hoping that war in Iraq could be avoided, but now it is upon us, we have to move very quickly," Mr. Lavanchy said.
Meanwhile, the Director-General of the World Health Organization (WHO), Dr. Gro Harlem Brundtland, made an appeal on behalf of the most vulnerable people in Iraq -- the elderly, women, children, and disabled. She warned that the most basic human rights to clean water or to basic health care could not be met, given the devastation of Iraq's infrastructure.
"We must do everything we can to mitigate this humanitarian disaster...to protect Iraq's most vulnerable citizens and respond with generosity and speed," she said in a speech delivered in Geneva, parts of which were read out during a UN humanitarian briefing in Amman, Jordan.
WHO said most basic needs included providing treatment and supplies for trauma and injury, preventing the outbreak of communicable diseases, providing fresh drinking water and sanitation, and efforts to minimize discontinuation of treatment for chronic illnesses in Iraq where, for example, 600,000 people suffer from diabetes.
The Food and Agricultural Organization (FAO) said the conflict came at a particularly bad time for both the winter crops, which are scheduled to be harvested in April and on which Iraqis depend for cereals, and spring crops, which are being planted right now and which provide essential vegetables.