The United Nations warned Monday of a quickly mounting death toll from the Philippines super typhoon with 10,000 feared killed in the worst-hit city of Tacloban alone.

The United Nations was "expecting the worst" over the final body count, one top UN humanitarian official said.

John Ging, UN humanitarian operations director, said 660,000 people had fled their homes because of typhoon Haiyan and that the United Nations will appeal for significant international aid for victims on Tuesday.

UN humanitarian chief Valerie Amos, who is heading for the Philippines, said in a statement that "local officials estimate that some 10,000 people were killed in one city alone." Her spokeswoman confirmed that she was referring to Tacloban, which was devastated by the storm.

"Many places are strewn with dead bodies," Ging told a news conference at UN headquarters, confirming estimates that "over 10,000 people perished."

When asked about the final toll, he added: "We are certainly expecting the worst. As we get more and more access we find the tragedy of more and more people killed in this typhoon."

Ging told of the battle to get to Tacloban and other areas badly hit by the super-typhoon, which swept huge waves and the fiercest storm winds recorded in the past century into the Philippines.

He said it was taking three hours for relief vehicles to cover the 11 kilometers (seven miles) from Tacloban airport into the city.

"The first priority of response teams, once they were able to navigate their way into these areas, is to mobilize the burial of dead bodies because of the public health issues," he said.

Ging added that there was a desperate need for clean drinking water and food for survivors.

Amos was expected in Manila to run a joint relief operation by the United Nations and private groups.

The United Nations has already released $25 million from its emergency fund for aid, and Amos and the Philippine government will on Tuesday launch a "flash appeal" for cash. UN officials said it was likely to be for hundreds of millions of dollars.

"The scale of devastation is massive and therefore it will require the mobilization of a massive response," Ging said.

The UN official praised the Philippines government response to the disaster as "very impressive."