Pakistan's National Disaster Management Authority said 422 people have been killed, 3,000 injured and about 5 million adversely affected by this year's monsoon rains and resultant flooding.
The worst-hit area is the southeast Sindh province where 239 deaths were reported, according to NPR.
A government spokesman told the BBC that Pakistan would not yet ask for international assistance.
"The government's point of view is that the situation will be handled from own resources," Ahmad Kamal told the AFP news agency.
Kristalina Georgieva, commissioner for international cooperation and crisis response, told AFP that flooding "in Pakistan [is] affecting tens of thousands of vulnerable people."
She added, "They are the victims of three consecutive years of devastating monsoon floods, which have destroyed livelihoods and left behind lingering food shortages and hunger."
UNICEF Pakistan Deputy Representative Karen Allen reaffirmed Georgieva's analysis, telling the BBC the 2012 crisis was compounded by years of consecutive flooding.
"Some of the affected children are living in areas that are experiencing devastating flooding for the second or third time over the past three years, and these new floods have disrupted their recovery," she said.