The United Nations said Monday it was withdrawing its international staff from northwestern Pakistan because of the security situation there. "They will be relocated. Immediately," Ishrat Rizvi, a UN spokeswoman, told AFP. UN Secretary General Ban Ki-moon declared a security condition known as Phase IV in the Northwest Frontier Province and Federally Administered Tribal Areas, a UN statement said. "The decision has been taken bearing in mind the intense security situation in the region," the statement said. Late last month the UN's World Food Programme (WFP) closed distribution centres serving more than two million people in the northwest because of security fears. The closure affecting the Swat Valley region followed a suicide bombing of the WFP compound in the capital Islamabad. That attack, also last month, killed five aid workers including an Iraqi national. Rizvi could not immediately say how many foreign staff would be evacuated. "We don't have big numbers of international staff in that region," she said.