United Nations Secretary General Ban Ki-moon asked the government of Zimbabwe on Thursday to immediately end the ban on international humanitarian assistance in the country, according to dpa. President Robert Mugabe, under attack for the violence in the presidential elections in May, retaliated by imposing severe restrictions on non-governmental organizations and private voluntary groups to assist large populations affected by the violence. In June, Ban asked Mugabe to lift the curbs on relief groups, but Mugabe did not reply. "These groups have a vital role in the delivery of humanitarian aid, including much-needed food assistance," Ban said in a statement. "Due to their inability to operate, only 280,000 people of the 1.5 million in need of food assistance are being reached with distributions." The statement said: "This ban must be lifted immediately so that aid organizations can carry out their relief work and avert a catastrophic humanitarian crisis." "I call on the government of Zimbabwe to fully respect humanitarian principles and the impartiality and neutrality of voluntary and non-governmental organizations, allowing them to operate freely and with unrestricted access to those in need."