The UN is dealing with so many international crises that Secretary-General Antonio Guterres's spokesman was last week asked if his boss ever felt like hiding under his desk.

“The world is in a mess,” was the spokesman's response to a list that included proliferation concerns in North Korea, a power struggle in Venezuela and the war in Syria.

But a corruption scandal in the World Health Organisation's operations in Yemen has highlighted that an increased role for UN agencies in global hot spots has left the world body facing questions about how it manages its own staff.

An internal report shows WHO employees diverted food, medicine, fuel and money away from those supposed to receive help.

More than a dozen UN workers sent to Yemen are accused of collaborating with combatants to benefit financially from billions of aid dollars flowing into the country.

Although the investigation continues, the conduct suggests that when aid operations are set up quickly the results will be disastrous.

“Any high-pressure humanitarian operation of this type is going to create space for bad actors,” a veteran UN analyst said.

“The WHO is institutionally less capable at managing these crisis situations than some other UN agencies, like the World Food Programme and the UN High Commissioner for Refugees.”

WHO internal auditors established that unqualified people were in high-paying jobs, millions of dollars were deposited in personal bank accounts, contracts were approved without paperwork and tonnes of donated medicine and fuel went missing, AP recently reported.

A second investigation is focused on another UN agency, Unicef, and a report that one staffer allowed a Houthi rebel commander to travel in a UN vehicle so that he could be protected from possible military attack.

The credibility of the UN's procedures, and its overall role, has been left in question.

Under WHO rules, aid money can be transferred directly into the personal accounts of staffers to speed up the purchase and delivery of goods in a trouble spot, even though the potential for abuse is obvious.

“The behaviour is egregious but with the entire humanitarian system facing budgetary and operational overstretch, it is almost inevitable that incidents like this will crop up regularly,” a former UN official said of the Yemen misconduct allegations.

The corruption probe comes at an especially bad time for the UN as its underfunded agency for Palestinian refugees, UNRWA, is under investigation for breaches of ethics.

Several countries have halted additional contributions to UNRWA and others are reviewing their donations.

The WHO scandal suggests that posting international staff to unstable countries such as Yemen, which has been long ranked high on international indexes for corruption, is a breeding ground for mismanagement.

With little knowledge of the country, UN officials have few choices but to link up with local organisations whose leaders may have no aim other than to enrich themselves.

The UN may be accused of acting too slowly if they do not establish such partnerships, even legitimate ones, but then be accused of incompetence if things go wrong.

And with often primitive banking systems to work with, the use of cash is usually necessary.

But this massively increases the risk of corruption and lessens the chances of effective auditing of donated resources.

Yemen has long been a difficult place to operate. It ranked 176 out of the 180 countries on Transparency International's Corruption Perceptions Index last year.

But even before political instability turned into conflict over the past decade, its officials were known to demand bribes or gifts from local and foreign companies in return for co-operation.

A UN Panel of Experts on Yemen has said that Houthi commanders in Sanaa have pressured aid agencies to employ loyalists and threatened to withdraw visas or disrupt international operations if they do not comply with rebel demands.

The UN's Office of Internal Oversight Services is handling the WHO probe.

The actions of Nevio Zagaria, an Italian doctor who led the Sanaa office for two years, are the main subject of the investigation, AP reported.

Dr Zagaria is said to have led much of the misconduct including staff appointments based on nepotism, questionable procurement practices and the use of staffers' bank accounts, including his own.

But he retired from the UN in September last year so he is unlikely to face any sanction other than an official censure.AFP