Heavy rain lashed the makeshift camps housing Pakistan's flood survivors Monday and authorities warned of more flooding this week, adding to 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 160,000 square kilometers (61,776 miles) of land _ about 1/5 of the country _ have been affected, the Associated Press reported. 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 around 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 1/2 meters) high in some places. He said that some 4,000 small villages had been either cut off or washed out. «Water is everywhere,» he said.