Nairobi — Somalia's hardline Islamist rebel group al Shabaab has ordered the UN food agency to halt all operations and leave the country, a statement from the rebels said today.

The World Food Programme's Somalia operation has faced several challenges in recent months including accusations of diversion of food by its workers to rebels. It dismissed the charges after its own internal investigations.

The rebel group accused WFP of delivering foods that are not fit for human consumption. "We realised that low grade foods have been laying in the stores, upon inspection," said the statement.

The statement also indicated that many of the foods could be highly injurious to health. "Many public ailments could be traced to foods brought in by WFP," said the document.

Al-Shabaab's announcement emphasised that the agency had used the items it delivered for political purposes. The Islamist movement accused WFP of feeding foreign and government troops.

"Effective as of today, all of WFP's operations inside Somalia are terminated and the organisation has been completely banned," al Shabaab said in the statement.

The group also said the agency's food distribution had negatively impacted local farmers

"All Somali persons, businessmen and truck drivers who are currently contracted to or working with WFP are hereby instructed to terminate their contracts immediately," the statement added.

Anyone found working with the agency after the order was issued would be considered an accomplice to the organisation's schemes and guilty of aiding in the destruction of the economy, al Shabaab said in the statement issued by its self-styled Office for Supervising the Affairs of Foreign Agencies. Asked about the order, Peter Smerdon, a spokesman for the World Food Programme in Nairobi, told Reuters:

"WFP is determined to help the people of Somalia in need of assistance, regardless of who controls the areas in which they live, as long as it is safe for our staff to do so." Al Shabaab had earlier ordered the agency to stop importing food for relief into the country and to source it from Somali farmers from the beginning of this year.

The UN Food Agricultural Organisation estimates that nearly half of the Somali population need aid and the country has the world's highest malnutrition levels.

Fighting in Somalia has killed at least 21,000 people and forced over 1.5 million from their homes since 2007.