Such is the number of international crises that the UN is dealing with 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.

A corruption scandal in the World Health Organization's operations in Yemen, however, 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 documents that 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 instead accused of collaborating with combatants to benefit financially from billions of aid dollars flowing into the country.

Although the probe is ongoing, the conduct in question 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,” said a veteran UN analyst on condition of anonymity.

“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.”

The Associated Press reported on August 5 that WHO internal auditors established that unqualified people were placed 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.

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 shielded from possible military attack.

The credibility of the UN's procedures, as well as its overall role, has been left in question. Under WHO rules, aid money can be transferred directly into the personal accounts of staffers, as a means 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,” said a former UN official 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 ethics violations. Several countries have halted additional contributions to UNRWA and others are reviewing their donations.

The WHO scandal suggests that the posting of international staff to unstable countries such as Yemen — long ranked high on international indexes for corruption — is a breeding ground for mismanagement.

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

The UN may be accused of acting too slowly on the one hand if they don't establish such partnerships, even legitimate ones, but then be cited for 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 previously said that Houthi commanders in Sanaa have pressured aid agencies to employ loyalists and threatened to withdraw visas or disrupt international operations if they don't comply with rebel demands.

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

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

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