The United Nations' World Food Program (WFP) today closed distribution centers serving more than two million people in northwest Pakistan over security fears. The move affecting the Swat Valley region comes after a suicide bomber attacked a WFP compound in the capital Islamabad, killing five aid workers this month. A spokesman for WFP in Islamabad said the agency closed all its food distribution centers in the region which are the humanitarian hubs for internally displaced people. He said the agency faced security problems and it was decided last night to close the centres. The spokesman said the closures were temporary and the decision would be reviewed later in the week.