Private charities that are buying freedom for enslaved children and young women in Sudan have reacted angrily to recent criticism of them from Unicef, the UN Children's Fund. "It is difficult to understand why Unicef should say our activities are intolerable," said John Eibner, head of Christian Solidarity International, of Zurich, which since 1995 has brought and set free 5,942 Sudanese children, spending about $50 a child.