A Briton and a Frenchman working for the UN Office on Drugs and Crime have been shot dead as they disembarked from a plane in central Somalia, officials and witnesses say.
The pair were shot on Monday inside the airport in Galkayo, a city straddling the border between Somalia proper and the northern self-proclaimed state of Puntland.
The al Qaeda-linked Shebab group, which has repeatedly attacked foreign targets in recent years, welcomed the killing but denied any responsibility.
The head of counter-piracy in Puntland told reporters that the two victims, whose names were not immediately released, were on a visit to discuss Somalia's controversial money transfer system.
France's President Francois Hollande confirmed that one fatality had been French, as he condemned the "cowardly assassination" of people "working, in the name of the international community, for peace".
"Both were working for the United Nations Office on Drugs and Crime (UNODC) to help deliver a better future for Somalia," British Foreign Secretary William Hague said in a statement, confirming that the other victim was a Briton.
In Washington, State Department spokeswoman Jen Psaki also condemned the killings and urged authorities "to fully investigate this crime and to bring the perpetrators to justice without delay".
"The United States and the United Nations remain determined to support the people and the federal government of Somalia in their efforts to strengthen peace, security, and the rule of law."
The motives behind the attack were not yet clear nor was there any confirmed report that any arrest had been made.
"Two white men have been shot inside the airport as they got off a plane," local security official Mohamed Mire said.
"One of them died inside the airport and the other one was rushed to hospital where he later died of the injuries," Hassan Ahmed, another witness, said.
A security source suggested the attack was carried out by one single gunman wearing a police uniform but a statement by UNODC spoke of "unknown gunmen".
Abdirazak Mohamed Dirir, the counter-piracy director in Puntland - which has been a stronghold for several pirate gangs plying the Red Sea and Indian Ocean over the past decade, said the slain pair were visiting to discuss the homegrown banking system.
The informal value transfer system known as Hawala channels huge amounts of remittances from Somalia's diaspora but has also been suspected of being used to fund the Shebab and organised crime in the region.
In February at least six people were killed when a suicide car bomb hit a UN convoy close to the heavily-fortified international airport in Mogadishu.
In June last year the Shebab also carried out a raid against a UN compound in the capital, killing 11 people.
A Shebab spokesman, Sheikh Ali Mohamed Rage, told AFP that the group was not behind Monday's killings but nevertheless described them as "the holy work of a patriot".
"Those who were killed were there for spying and their killing is very much welcome," he said.
