Somalia\'s Islamist Shebab rebels ordered 16 international aid agencies shut on Monday in areas they control after armed raids on several offices, and warned more would follow if they did not toe the line. Witnesses and aid workers reported that Shebab gunmen stormed the offices of several agencies in apparent coordinated raids in rebel-controlled regions in Somalia, an area gripped by what the United Nations says is the world\'s worst humanitarian crisis. \"Any organisation found to be supporting or actively engaged in activities deemed detrimental to the attainment of an Islamic State, or performing duties other than that which it formally proclaims, will be banned immediately without prior warning,\" the Shebab said in a statement. Six United Nations organisations were ordered closed by the Shebab, including the agencies for refugees (UNHCR) and children (UNICEF), as well as the World Health Organisation (WHO) and the UN Population Fund (UNFPA). It also barred the UN Office for Project Services (UNOPS) and the Food Security and Nutrition Analysis Unit (FSNAU). \"Three armoured vehicles with gunmen surrounded the offices, including the office of UNICEF,\" said Adulahi Idle, a resident in the city of Baidoa. \"I saw many militiamen go inside the places and force the people there to leave and the men took control.\" It leaves just a handful of aid agencies able to operate in rebel-held areas, including the International Committee of the Red Cross (ICRC) and Medecins Sans Frontieres, and risks worsening the crisis there further. The UN has warned that nearly 250,000 people face imminent starvation in southern Somalia, the main base for the hardline Shebab, with several areas under famine or emergency conditions.  The Al-Qaeda-linked group accused the agencies of \"lacking complete political detachment and neutrality... thereby intensifying the instability and insecurity gripping the nation as a whole.\" The Shehab also said the groups were working to \"foster secularism, immorality and the degrading values of democracy in an Islamic country,\" and accused them of \"amplifying the refugee crisis.\" UNICEF official Marixie Mercado confirmed that their office in Baidoa had been occupied by Shebab insurgents, adding the agency was \"extremely concerned about the impact on our humanitarian operations.\" A regional security source said the raids in south and central Somalia were well planned and coordinated, with gunmen seizing computers, telephones and other equipment from aid workers. No arrests were reported. \"It was a surprise, but something that was clearly planned,\" said an aid agency official working in Somalia. \"They came with guns into the offices of two aid agencies and ordered all the staff to go home, and have taken control of the offices,\" said a local resident working for an international aid agency in Dinsor, in Bay region. Other aid agencies affected include the Norwegian Refugee Council (NRC), Danish Refugee Council (DRC), Concern, Norwegian Church Aid (NCA) and the Italian Cooperazione Internazionale (COOPI). The Shebab also shut down the Swedish African Welfare Alliance (SAWA), the German Technical Cooperation (GIZ), Action Contre la Faim (ACF), Solidarite and Saacid. \"We are concerned that this will create a vacuum in supplies of basic services for the people,\" said the head of one aid agency involved, asking not to be named to protect the group\'s employees in Somalia. The extremist Shebab imposes draconian rules on humanitarian workers and has blocked international staff working for aid agencies in its areas, but has allowed limited operations by Somali nationals. Regional powers have been increasing military pressure on the Shebab, with Kenyan forces in the far south, Ugandan and Burundian African Union forces in Mogadishu, and Ethiopian troops arriving earlier this month from the west. Meanwhile a suspected bomb blast rocked the main hospital in the war-torn capital, the latest in a string of attacks in Mogadishu since the Shebab abandoned fixed positions there in August and switched to guerrilla tactics. Three people were wounded by the blast late Sunday in the hospital, which provides life-saving care for severely malnourished children struggling from ongoing famine in the city\'s crowded camps for displaced people.