UN Secretary-General Kofi Annan warned Wednesday that a second "massive wave of death" will hit Pakistani areas most affected by the mammoth earthquake unless the international community immediately escalates the relief effort. With winter approaching fast and terrain difficult in the affected area of some 28,000 square kilometers (11,000 square miles), the relief effort is one of the most challenging ever undertaken, he said. "It is a race against time to save the lives of these people," Annan said. "This is a huge, huge disaster ... perhaps the biggest ever that we have seen ... and at the time of the cold season." He called for a major increase in funds, noting that donors have only made firm commitments for 12 percent - or $37 million (â‚¬31 million) - of the UN appeal for $312 million (â‚¬261 million). By comparison, he said, the UN flash appeal after last December's tsunami was more than 80% funded within 10 days of the disaster.