(CNN) -- Three gunmen shot and killed a United Nations staff member in southern Somalia on Sunday, the U.N. Children's Fund said Monday.
The gunmen shot Mukhtar Mohammed Hassan, a water engineer, at close range as he and friends were walking into town in Huddur after they attended a mosque, UNICEF said in a written statement.
Before they shot Hassan, the gunmen had fired shots into the air to disperse others nearby, the agency said, citing reports.
He was shot three times, a World Food Programme official told Shabelle news agency.
Investigations into the murder are under way, UNICEF said.
Hassan helped provide technical supervision for UNICEF-supported water, sanitation and hygiene activities in central and southern portions of the Horn of Africa nation, the organization said.
"Mukhtar played an important role in providing vulnerable communities with access to clean drinking water and sanitation in areas where the risk of water-based diseases is high," UNICEF Deputy Representative Hannan Sulieman said.
"UNICEF condemns this senseless killing of a staff member."
U.N. Secretary-General Ban Ki-moon also condemned the killing, his spokeswoman Michele Montas said Monday.
Last month, a WFP aid worker was killed in Somalia after being abducted during an off-duty weekend visit to his home in Dinsor.
Abdulkadir Diad Mohamed, 33 -- a Somali national -- and the driver of the vehicle in which he was traveling were killed as they tried to escape, the statement said. A third member of the group successfully got away, it said.
The Red Cross warned earlier this year that Somalia faces the worst famine since the early 1990s. The country's continual armed conflicts in central and southern Somalia have aggravated the situation, hindering people from accessing shelter and medical attention.