SUKKUR, Pakistan - Angry flood survivors in Pakistan blocked a highway to protest slow delivery of aid and heavy rain lashed makeshift housing 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 (160,000 square kilometers) 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 came to hand out food when media were present. "They are throwing packets of food to us like we are dogs. They are making people fight for these packets," he said. The Sindh irrigation minister, Jam Saifullah Dharejo, said the dam in Sukkur faced a major test of its strength as floodwaters coursed down the Indus River into Pakistan's highly populated agricultural heartland. "The coming four to five days are still crucial," he said. 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. He urged the international community to speed up assistance. The world body has appealed for an initial $460 million to provide relief, of which about 60 percent has been given. The latest flooding over the weekend hit a poor region on the border between Sindh and Baluchistan provinces. Sher Khan Bazai, the top government official in Nasirabad district, said 25,000 families had been made homeless by waters 8 feet (2.5 meters) high in some places. About 4,000 small villages had been either cut off or washed out. "Water is everywhere".