ISLAMABAD -- Devastating floods in Pakistan's worst-hit province have killed 17 more people in the past 48 hours, including nine children, officials said Wednesday as the for US$39 million to help the most vulnerable flood victims.

Only a third of the sum in the funding appeal has been met so far, UNICEF said in a statement. Pakistani doctors and medical workers are struggling to contain the outbreak of waterborne diseases, malaria, and dengue fever among hundreds of thousands of survivors now living in tents in southern Sindh province.

The unprecedented monsoon rains and flooding, which many experts attribute to climate change, have affected 33 million people and caused at least 1,576 deaths and 12,862 injuries across the country since mid-June.

Of that number, 707 people -- including 297 children and 132 women -- have died in Sindh, where many areas remain submerged. Hollywood actress and U.N. humanitarian Angelina Jolie made a surprise visit to Sindh on Tuesday, meeting with some of the flood victims.

UNICEF said more than 3.4 million children have been uprooted from their homes and the floodwaters have claimed the lives of more than 550 children across Pakistan.

"Without a significant surge in support, we fear many more children will lose their lives," UNICEF said in a statement.

In Sindh, many of the roads and bridges have been washed away or are badly damaged, and thousands of families remain cut off and desperately need support. "Families have no food, safe water or medicines," the agency said.

UNICEF has set up 71 mobile health camps and temporary schools for children in the flood-affected areas. But its $39 million appeal is still less than a third funded, UNICEF added. That sum is part of U.N.'s flash appeal for $160 million to support Pakistan's flood response.

Meanwhile, Pakistani Prime Minister Shahbaz Sharif met with world leaders on the sidelines of the U.N. General Assembly, seeking more help from the international community to tackle the record-breaking floods.

In a televised message from New York, Sharif on Wednesday urged philanthropists to urgently and generously donate baby food for children affected by the floods. "God will reward you for this noble work," he said.

The United Nations on Wednesday expressed its concern over increasing cases of waterborne diseases among floods survivors. "We are deeply worried about the very real possibility of a wave of death and disease which is already stretching its tentacles. A second disaster is looming in sight," the U.N. said in a statement.

It said over 134,000 cases of diarrhea and 44,000 cases of malaria were reported in the flood-hit area of Sindh just this past week.

"Millions of children are still grappling to survive, and we fear thousands will not make it," the U.N. said, adding that 6 children had died the previous day in Sindh.

Pakistan's infrastructure and agriculture have also been decimated, raising concerns for a looming food crisis. Authorities say the damage caused by the floods amounts to at least $30 billion.