(Adds African Union statement, Nigerian comment)
MOGADISHU, Jan 6 (Reuters) - A roadside bomb killed a Ugandan soldier in Somalia's capital on Tuesday and masked gunmen murdered a man working for the United Nation's World Food Programme in the southwest of the Horn of Africa nation.
The killings come as Ethiopian troops who have been propping up an interim government and fighting Islamist insurgents for the past two years are pulling out of Somalia, saying their mission has been accomplished.
The withdrawal has fuelled fears of a power vacuum in a country where violence and chaos onshore have allowed piracy to flourish in the busy shipping lanes off Somalia's coast.
More than 16,000 civilians have been killed since the insurgency started two years ago, a million Somalis have been displaced and a third of the population relies on food aid.
The African Union's top diplomat, Jean Ping, said he was particularly concerned about the precarious security situation and urged the U.N. Security Council to approve support urgently so an African peacekeeping force in Somalia can be bolstered.
The African Union wants to deploy some 2,500 troops from Uganda, Burundi and Nigeria to replace the Ethiopian soldiers but financial and logistical hitches have delayed the plan.
"The commission is making every effort to ensure that the additional battalions from Uganda and Burundi are deployed as soon as possible," said Ping, chairman of the AU Commission.
RULES OF ENGAGEMENT
Nigerian defence spokesman Chris Jemitola said Nigerian troops were ready, but the terms of engagement for the mission needed to be decided by politicians first.
"Detailed instructions have still not been issued," he said.
Uganda and Burundi have called for a stronger mandate to let its 3,200 peacekeepers protecting strategic sites in Somalia go on the offensive against any insurgents preparing attacks.
Ping said the AU was considering strengthening the mandate. He said Algeria was ready to help the extra troops deploy and Egypt had also offered logistical support.
A Ugandan soldier died and another was wounded when a convoy of peacekeepers was hit by an improvised explosive device on the outskirts of Mogadishu, Major Barigye Ba-Hoku, spokesman for the small AMISOM force, told reporters.
A World Food Programme food monitor, Ibrahim Hussein Duale, was shot dead by three masked gunmen at a school on Tuesday near a town in the southwestern region of Gedo, the WFP said.
"We call on all parties to allow us to do our job -- providing food to feed the hungry at this critical time," said WFP Executive Director Josette Sheeran in a statement.
International interest in solving the crisis in Somalia has risen since a surge in piracy last year that earned the bandits millions of dollars in ransoms and shocked shipping firms.
French forces handed over 19 more captured pirates to Somali authorities on Tuesday as international navies stepped up their efforts to stamp out the hijackings.
But the commander of the European Union naval task force in the region said increased patrols would not be enough.
"Piracy cannot be eradicated fully by naval units. We need a political solution in Somalia which has to deal with peace restoration, law and order in Somalia," Commodore Antonios Papaioannou told Reuters in Kenya's port of Mombasa. (Additional reporting by Abdi Guled and Ibrahim Mohamed in Mogadishu, Mohamed Ahmed in Baidoa, Abdiqani Hassan in Bosasso, Celestine Achieng in Mombasa, Nick Tattersall in Lagos, Wangui Kanina and David Clarke in Nairobi; Writing by by David Clarke; Editing by Charles Dick)
Our Standards: The Thomson Reuters Trust Principles.