Aid workers might see themselves as neutral providers of relief but in heavily polarised conflicts they are almost inevitably accused of bias, putting their operations and staff at risk.
In conflicts such as Iraq and Afghanistan, Western aid workers are at risk because of perceived alignment with coalition forces, while elsewhere in the world, from Ethiopia to Sri Lanka, governments accuse them of backing insurgents.
Some professionals say Christian relief groups are suspected in many Islamic countries of proselytising under the guise of aid work, further complicating the job of relief workers.
"Because of the so-called war on terror, aid tends to be more politicised -- or considered to be more politicised," said Overseas Development Institute research officer Samir Elhawary.
"I think there has been a shift in which aid organisations are realising they have to be more aware."
Aid workers say it has always been difficult to prove neutrality and avoid accusations of bias. But the stakes today are higher with the cost of perceived bias measured in kidnapped and killed staff, compounds overrun or bombed, and access to needy populations denied.
Iraq has been left almost entirely off-limits to foreign aid staff after high-profile attacks on the Red Cross and U.N. compounds, while parts of Afghanistan are no better. A number of foreigners - many relief workers - have been abducted.
Some, such as most of the South Korean Christians taken by the Taliban, have been released. But the bullet ridden corpses of others have been left by the side of the road.
In 2006, 85 aid workers - almost all of them local staff - were killed worldwide, the highest since 2003 when numbers were swollen by the bomb attack on the U.N. compound in Baghdad that killed 22.
Aid workers complain that the involvement of coalition forces in rebuilding efforts causes confusion and means Western aid groups are no longer seen as neutral.
In May, Norway's army agreed to stop using white four-wheel-drive vehicles for their military reconstruction teams in Afghanistan after aid groups feared insurgents might mistake their own vehicles for those of NATO forces.
But more broadly, with Western aid groups mainly funded by Western governments who are themselves combatants in Afghanistan, perceived bias may always be a risk.
In war zones where Western states are not so directly involved - and even occasionally where they are - though operating on both sides of the lines aid workers are just as likely to be accused of backing rebels.
In July, Ethiopia expelled the International Committee of the Red Cross (ICRC) from its Ogaden region, accusing it of consorting with ethnic Somali insurgents. The Red Cross says it was acting well inside its neutral remit.
Rights workers say Ethiopia is fighting a brutal counterinsurgency campaign in the region and restricting food deliveries, while the rebels accuse the government of trying to create "man-made famine". Aside from a handful of aid workers, there are few outside observers.
Analysts and aid workers say sometimes governments and insurgents simply do not want outside relief groups interfering - or witnessing what might be going on.
Aid agencies in the world's largest humanitarian operation in Sudan's Darfur region say they are no longer able to talk publicly about the situation, leaving campaigning to advocacy groups without staff on the ground.
Even then, the Sudanese government can be sensitive. At the weekend, it kicked out CARE International's country director after an internal CARE report became public.
Experts say governments almost invariably suspect aid groups that feed populations amongst which rebels move.
Governments fear relief groups are legitimising rebels by working with them and some say that through providing the sort of health, social and relief services government would normally provide in rebel areas they effectively help insurgent groups.
In Sri Lanka, government officials frequently accuse aid agencies of either deliberately or accidentally supporting the Liberation Tigers of Tamil Eelam (LTTE).
Nordic ceasefire monitors blamed the government for the massacre of 17 local aid workers last year - a charge the government denies. Several senior officials accuse aid workers of being bribed by the LTTE.
In an ethnic war such as Sri Lanka, governments tend to suspect aid workers from the same ethnic group as rebels. Almost all aid workers killed in Sri Lanka have been Tamil.
Relief group security officers say tracking the loyalties of local staff is difficult, and some may inevitably be drawn into a conflict. But they say they try to guard against it.
Ultimately, humanitarian workers say dealing with groups or governments whose purposes and methods they might disagree with is necessary if the needy are to be helped.
The Red Cross - one of the few aid groups that talks to normally ostracised groups such as the Taliban or Colombia's FARC - says there is no one they would not talk to.
"If you are going to reach people and give them aid and relief, you have to deal with the groups that control access," said ODI's Elhawary.
"It's about being really aware and understanding what the different dynamics are."
