SUKKUR, Pakistan — Angry Pakistanis blocked a highway to protest slow delivery of aid, and rain lashed makeshift housing on Monday as a forecast of more flooding increased the urgency of the massive international relief effort.
Pakistan's worst floods in recorded history began more than two weeks ago in the mountainous northwest and have spread throughout the country. Some 20 million people and 62,000 square miles of land — about one-fifth of the country — have been affected.
The scale of the disaster has raised concerns it could destabilize the country, which is pivotal to U.S. hopes of defeating al-Qaida and the Taliban.
Hundreds of victims blocked a major highway with stones and garbage near the hard-hit Sukkur area, complaining they were being treated like animals. Protester Kalu Mangiani said government officials only handed out food with media present.
"They are throwing packets of food to us like we are dogs. They are making people fight for these packets," he said.
The U.N. children's agency warned that 3.5 million children were at high risk of deadly waterborne disease such as diarrhea and cholera. U.N. Secretary-General Ban Ki Moon flew over the flood-hit area Sunday and said he had never seen a disaster on such a scale.
The world body has appealed for an initial $460 million to provide relief, of which about 60 percent has been given.
Britain's deputy prime minister, Nick Clegg, accused some nations of failing to offer sufficient support.
"The response from some sections of the international community has been lamentable," Clegg said, without naming the countries.
Britain's government has so far provided $26 million in emergency aid in response to the floods, making it one of the largest foreign donors.
The latest flooding hit a poor region on the border between Sindh and Baluchistan provinces.
Sher Khan Bazai, a government official, said 25,000 families had been made homeless by waters 8 feet high in some places. About 4,000 small villages had been either cut off or washed out.
"Water is everywhere," he said.