"Of that number, an estimated 600,000 people need immediate help to deal with the winter, particularly in the north," Xinhua quoted Dujarric as saying at a daily press briefing.
UN agencies and their partners urgently require approximately $172 million to help the most vulnerable IDPs, to get shelter, food and core relief items and health services, he said.
"The Food and Agriculture Organisation (FAO) says that through funding from the Kingdom of Saudi Arabia and in partnership with non-governmental organisations, will start distributing 3,000 metric tonnes of wheat seeds and 3,000 metric tonnes of fertilizers in conflict-affected areas of Iraq next week," he said.
"This will benefit more than 15,500 farming families in Nineveh, Erbil and Dohuk governorates in Iraq."
Iraq has been convulsed by increasing instability over the past several months amid an ongoing offensive by the Sunni radical group Islamic State, unleashing wave after wave of internally displaced people and refugees.
Just last week, an IS offensive against the Iraqi town of Hit prompted an estimated 180,000 people to flee the violence.
According to the Office of the UN High Commissioner for Refugees (UNHCR), many of those displaced were now sheltering with relatives and friends as well as in schools, mosques and public shelters already overwhelmed by Iraq's mounting population of displaced people.