Somalis have been forced to flee fighting in huge numbers
An engineer working for the UN in Somalia has died in the latest of a series of assassination-style killings of aid workers.
The Somali official, employed by UN childrens' fund, Unicef, was shot several times in the head and then the body, intelligence sources said.
Somalia has been wracked by conflict since 1991 and is now facing an Islamist and nationalist insurgency.
It is not clear which group is behind the targeted assassinations.
The latest targeted killing took place in the southern town of Hudur.
Two days earlier, another UN aid worker was killed in a similar way in the coastal town of Merka.
Intelligence sources, who asked not to be named, said the cold-blooded assassination of aid workers by trained killers had become the norm in the past four months, the BBC's World Affairs correspondent Mark Doyle reports.
He says head shots, followed by bullets to the chest, are now the chillingly familiar method.
The UN co-ordinator for Somalia, Mark Bowden, said that with 28 aid workers killed in the country over the past year, it had become one of the most dangerous places in the world for humanitarian staff.
In recent months, all of those killed have been Somali nationals because most foreign humanitarian workers have left the country.
The current Somali government is internationally recognised but has lost control of large parts of the country to an insurgency driven by Islamist and nationalist groups.
The government is backed by troops from neighbouring Ethiopia, who are deeply unpopular with many Somalis.
More than three million people in Somalia - almost half the population - are in acute need of food or medical aid, according to the UN.