(CNN) -- A mine exploded Monday on a road in southern Somalia, killing four people -- three members of the medical humanitarian group Medecins Sans Frontieres and a journalist.
Ongoing violence in Somalia has devastated the capital Mogadishu.
The incident occurred Monday along a road in Kismayo, the group said.
Victor Okumu, 51, a Kenyan doctor; Damien Lehalle, 27, a French logistician; and a Somali driver named Billan were the MSF workers who were killed.
Another member of the team was slightly wounded, the group said in a posting on its Web site.
"The exact circumstances of this fatal incident are not yet clear," the posting said.
Also killed was journalist Hassan Kafi Hared, 36. The remote-controlled mine erupted as he was walking to a news conference in Siyad Village in northern Kismayu, said the National Union of Somali Journalists (NUSOJ).
He was working for the government-run Somali National News Agency and a Somali Web site called gedonet.com. He is survived by a wife and three children.
"This is a targeted attack and we declare that this brutal killing on the journalist and the aid workers is an attack on the society itself," said NUSOJ Secretary General Omar Faruk Osman, in a news release.
"We demand that transitional government and the authorities in Kismayu to identify the culprits of this crime and bring them to justice" he said.
The medical humanitarian organization said it was evacuating remaining international members of it staff from Kismayu.
Hared is the second journalist to be killed this year, according to the Committee to Protect Journalists. The first, 38-year-old Norwegian reporter Carsten Thomassen, died Jan. 15 in a suicide bomb attack in Kabul.
In a written statement, a representative of U.N. Secretary-General Ban Ki-Moon said he condemned the killings and "demands a thorough investigation by the authorities." E-mail to a friend