The UN has declared its highest level of emergency in Iraq as a humanitarian crisis follows the rapid advance by Islamic State militants in the north.
Kurdish officials in Dohuk province said some 150,000 refugees were in the area, overwhelming the local population who were trying to feed them.
Meanwhile the US says it is unlikely there will be a rescue mission to help thousands who have fled to Mt Sinjar.
However the US vowed to continue to provide humanitarian assistance there.
The UN estimates that 1.2 million Iraqis have been internally displaced by the crisis.
The three other countries that have the same emergency status are Syria, South Sudan and the Central African Republic.
SPEEDING UP RESPONSE
The declaration by the UN of "Level 3 Emergency" would "facilitate mobilisation of additional resources in goods, funds and assets to ensure a more effective response to the humanitarian needs of populations affected by forced displacements", said UN special representative Nickolay Mladenov.
The situation of displaced people on Mount Sinjar remained critical, he said.
The UN had estimated that tens of thousands of people, most from religious minorities, were besieged on the mountain after being forced to flee their homes, including members of the Yazidi sect.
US forces conducted a brief mission to Mt Sinjar to assess the situation after days of international concern.
It found fewer people than expected and that those remaining were also in a better condition than feared - partly because thousands had left the mountain each night over the past days.
Planes have been dropping aid supplies on Mount Sinjar for several nights.
The US said it conducted its seventh air-drop of food and water on Wednesday, and had delivered more than 114,000 meals and 35,000 gallons (160,000 litres) of drinking water to those trapped.
The US has also continued to conduct air strikes on IS targets in Iraq's north.
France says it will arm Iraq's Kurds, who are already getting US military aid to fight IS. Meanwhile, the UK has pledged to join a rescue mission for displaced civilians.
The rapid advance across Iraq by Islamic State fighters has thrown the country into chaos.
On 29 June, IS said it had created a caliphate, or Islamic state, stretching from Aleppo in Syria to the province of Diyala in Iraq.