The first World Humanitarian Day highlights the perils faced by international aid workers in ever-edgier political situations.

Today is the first-ever World Humanitarian Day, an opportunity to reflect on how far we have come towards the ideal that everyone in need should be helped - regardless of nationality, race, religion or politics. It is a remarkable achievement that when crisis strikes today, it is taken for granted that aid workers will be on the scene within hours.

Yet if everyone agrees about the worth of humanitarian action, sadly the aid workers themselves - the men and women of courage who feel it is their duty to help people and give hope to millions - are increasingly under fire. This has grave implications for our work and the survival of those who rely on us.

Unfortunately, the need for humanitarian relief continues to grow. The causes of human suffering have multiplied over the years at least as fast as humanitarians have found ways to meet them. Though the number of conflicts around the world has shrunk over the last 20 years, the humanitarian fallout of conflict remains appallingly high. The kind of internal conflict we see so often these days is particularly ruinous for civilian lives and livelihoods.

Major developments in Sri Lanka and Pakistan in the first six months of this year have strained our humanitarian aid system to the limit. An estimated 2 million people have been displaced in Pakistan during the past few months - the fastest displacement of people in recent memory and, certainly, in Pakistan's history. In Sri Lanka, though the guns have finally and thankfully fallen silent, nearly 300,000 people are still in camps with little or no freedom of movement, waiting anxiously for the possibility of returning home and depending on assistance to survive until they do.

Meanwhile, long-running conflicts such as those in Darfur, the occupied Palestinian territory and Somalia continue to affect millions. The humanitarian operation in Darfur, the largest in the world and now in its fifth year, struggles to provide assistance to 4.75 million conflict-affected civilians. In Somalia, 3.25 million people desperately need help: an almost 50 percent increase from last year, in the most difficult and dangerous circumstances imaginable.

Natural hazards, ramped up in their ferocity and frequency by climate change, have had horrific consequences for many of the poorest people, particularly in Asia, in recent years. Cyclone Nargis in Myanmar last year killed 140,000 and left up to 2 million people desperately requiring humanitarian relief to get through the following months. In Central America, the annual hurricane season is leaving ever greater swathes of poor countries devastated every year. Inevitably, it is the poorest people in the poorest, least prepared countries who suffer the most.

Add to the mix new threats to livelihoods posed by chronic poverty, the food and financial crises, water and energy scarcity, migration, population growth, urbanisation and pandemics, and it is clear why humanitarian needs are growing in ways never previously envisaged.

Aid workers are used to overcoming the climatic, geographic, infrastructural and logistical difficulties involved in getting massive quantities of relief to people in some of the most remote or hard-to-reach places on earth. The speed and predictability with which aid can be delivered today, proved yet again this year in Pakistan, is testament to the remarkable work of many dedicated humanitarians.

But without the consent of the states involved - and increasingly, of non-state armed groups that control the territory we need to reach - that expertise counts for little. And increasingly today, that acquiescence for humanitarian access is lacking. Intentionally or accidentally, when the delivery of humanitarian assistance is restricted, lives are lost and misery prolonged needlessly.

I'm most of all saddened and increasingly horrified by the rising attacks on aid workers. Though humanitarians have always recognised the difficulties and dangers of what they do - the risk of being caught up in events or being in the wrong place at the wrong time - the attacks on them are increasingly targeted. We are too often being attacked either for what we have (as in Darfur or Chad, where banditry is rife and largely unchecked), or even worse for who we are (as in Somalia, Afghanistan and, this year, Pakistan, where four UN aid workers have been killed in as many months). The last two years have been successively the most deadly for aid workers on record. UN and NGO flags and emblems have too often come to be no longer protections but provocations.

On this day, August 19, in 2003, the UN offices in Baghdad were blown up by a truck bomb. Twenty-two humanitarian workers and dedicated professionals lost their lives, among them Sergio Vieira de Mello, a lifelong humanitarian who had saved lives and reduced suffering in some of the toughest places on earth.

So on this inaugural World Humanitarian Day, while we celebrate all that has been achieved, let us also remember the huge challenges in front of us from rising needs, do more to ensure that the basic humanitarian principles of independence, impartiality and neutrality are respected, and act to keep humanitarian workers safe.

John Holmes is the United Nations undersecretary-general for humanitarian affairs and emergency relief coordinator.