NAIROBI, July 9 (Reuters) - Gunmen have murdered another driver working for the U.N.'s World Food Programme in southern Somalia, the humanitarian agency said on Wednesday.

Ahmed Saalim was the fourth WFP-contracted driver to be killed in the anarchic Horn of Africa nation this year. WFP said he was caught in crossfire during fighting between his convoy's guards and militiamen near Leego village on Monday.

"WFP food is reaching many people but our drivers are daily risking their lives to deliver it," Peter Goossens, WFP Somalia country director, said in a statement. "We send our condolences to the family ... and appeal for these killings to stop."

Fighting between the interim government and Islamist insurgents has triggered a humanitarian crisis in Somalia that aid workers say may be the worst in Africa.

At least a million people have been uprooted by the violence since early last year, and their plight has been compounded by record high food prices, hyper-inflation and drought.

WFP said experts fear the number of Somalis needing food aid could reach 3.5 million people later this year -- nearly half the country's population. (Writing by Daniel Wallis; Editing by Mariam Karouny) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

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