The UN on Monday condemned the killing of the UN Development Programme's (UNDP) top official in Somalia, who was shot as he left a mosque near his home in the capital, Mogadishu.
Osman Ali Ahmed was shot by three men with pistols Sunday evening in Bula Hubey, south Mogadishu, witnesses told DPA.
"Osman Ali Ahmed was a highly respected UNDP staff member who had performed his duties with great courage and commitment over the past 14 years," Mark Bowden, UN resident and humanitarian coordinator for Somalia, said in a statement.
The US State Department condemned the "brutal" slaying and offered sympathies to Ahmed's family.
"Ahmed's murder ... highlights the determination of violent extremists to attack the right to worship and to silence moderate voices working for peace and lasting stability in Somalia," US spokesman Sean McCormack said.
Aid workers have been increasingly targeted for attacks and abduction since the man believed to be Al Qaeda's top operative in Somalia, Aden Hashi Ayro, was killed on May 1 in a US airstrike.
Ayro was the leader of Islamic militant group al-Shabaab, the armed wing of the Union of Islamic Courts (UIC). Al-Shabaab said it would target foreign troops and workers to avenge Ayro's death.
The chief of the UN refugee agency UNHCR's Mogadishu programme was recently abducted and is still being held.
Several other aid workers have been held captive for months, and the World Food Programme has seen three of its drivers slain this year.
"If this is indeed another example of a targeted killing of UN and non-UN humanitarian and development workers in Somalia, it is particularly outrageous and worrying at this critical time, when the need for humanitarian assistance is rapidly increasing," Bowden said.
The UN said that it was taking urgent measures to protect staff working Somalia, which is in the grips of a humanitarian crisis.
A combination of conflict, drought and rising food and fuel prices have left millions of Somalis dependent on humanitarian aid. Bowden said that aid work would continue despite the increasing danger to UN staff.
Militants have been waging a guerrilla war against government troops since the UIC was ousted from power at the beginning of 2007 with Ethiopian assistance.
The interim government has been unable to achieve stability in the Horn of Africa country, which has been plagued by chaos and civil war since dictator Mohamed Siad Barre was toppled in 1991.
A peace deal was agreed between moderate Islamists and the government in early June, but al-Shabaab has not signed the agreement and has vowed to keep fighting until Ethiopian troops leave Somalia.