Landslides have cut off large portions of Pakistan's Swat Valley and hampered efforts to help the 15 million people affected by Pakistan's worst flooding in decades.
Many roads and bridges have been washed away by the floodwaters, and heavy rains are preventing helicopters from taking off.
The United Nations has described the flooding, that has killed an estimated 1,600 people nationwide, as the worst natural disaster in years.
"This disaster is worse than the tsunami, the 2005 Pakistan earthquake and the Haiti earthquake," Maurizio Giuliano, a spokesman for the UN Office for the C-oordination of Humanitarian Affairs, said.
"Those who need humanitarian assistance here are certainly more than those needing assistance in any of the other three disasters," Giuliano told Al Jazeera on Monday.
Yousuf Raza Gilani, the Pakistani prime minister, visited Sindh province on Sunday and said that "millions of people have suffered, and still there is more rain, and further losses are feared".
"I appeal to the world to help us. We are doing what we can," he said.
"The government has done everything possible, but it is beyond our capacity, we are facing an extremely difficult situation."
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But residents in Swat, in northwestern Pakistan, have complained of worsening food and fuel shortages as the crisis drags on.
"There is no petrol in the pumps and no food in the shop," said Malik Amir Zada, a Swat resident, in a telephone interview with the AFP news agency.
"The government is doing nothing for us."
Rescue workers have rushed to evacuate thousands of families from the southern part of Sindh province, where floodwaters could burst the banks of the Indus river.
Food prices are expected to rise as the waters continue to swamp agricultural areas.
Pakistan's Express-Tribune newspaper reported "skyrocketing" fruit and vegetable prices on Sunday.
timeline
July 22: Floods first hit the western province of Balochistan, killing dozens.
July 27: Rains move north to Khyber Pakhtunkhwa; death toll tops 1,000.
August 2: Waters hit Punjab, submerging homes and farms.
August 6: Floods move south again, towards Sindh province.
"Floods and rains have made these things unaffordable," one shopper in Lahore told the newspaper.
Millions of acres of crops have been destroyed in Punjab province, often called the "rice bowl" of Pakistan, and across the northwest.
The flooding has also caused extensive damage to Pakistan's electrical infrastructure, forcing power plants to shut down across the country.
Pakistan already suffers from a crippling electricity crisis, with hours-long blackouts a daily occurrence.
More than 252,000 homes have been damaged or destroyed across Pakistan, according to the government.
Pakistan's military said over the weekend that it has rescued more than 100,000 people from flooded areas.
'Zardari's Katrina'
Asif Ali Zardari, Pakistan's president, is expected to return to the country on Monday or Tuesday after a visit to France and the United Kingdom.
FLOOD STATISTICS
1,600 killed
Four million left homeless
15 million displaced or affected
558,000 hectares of farmland underwater
The trip, at the height of the disaster, was criticised by many Pakistanis, who accused Zardari of mismanaging the crisis.
Fatima Bhutto, Zardari's estranged niece, called the flooding "Zardari's Katrina", a reference to George Bush's, the former US president, handling of Hurricane Katrina in 2005.
Many villagers have complained about a lack of basic services in relief camps established by the government and the Pakistani army.
The army has about 300,000 troops working on the relief effort, but some human rights activists are concerned that the military is undermining civilian institutions.
"Yes, it is the military's job to take care of the rescue, but the civil administration must be strengthened and properly organised," Hina Jilani, a Pakistani supreme court advocate, told Al Jazeera.
Jilani said that local communities need to play a larger role in the response.
Many roads and bridges have been washed away by the floodwaters, and heavy rains are preventing helicopters from taking off.
The United Nations has described the flooding, that has killed an estimated 1,600 people nationwide, as the worst natural disaster in years.
"This disaster is worse than the tsunami, the 2005 Pakistan earthquake and the Haiti earthquake," Maurizio Giuliano, a spokesman for the UN Office for the C-oordination of Humanitarian Affairs, said.
"Those who need humanitarian assistance here are certainly more than those needing assistance in any of the other three disasters," Giuliano told Al Jazeera on Monday.
Yousuf Raza Gilani, the Pakistani prime minister, visited Sindh province on Sunday and said that "millions of people have suffered, and still there is more rain, and further losses are feared".
"I appeal to the world to help us. We are doing what we can," he said.
"The government has done everything possible, but it is beyond our capacity, we are facing an extremely difficult situation."
Shortages
Special coverage
But residents in Swat, in northwestern Pakistan, have complained of worsening food and fuel shortages as the crisis drags on.
"There is no petrol in the pumps and no food in the shop," said Malik Amir Zada, a Swat resident, in a telephone interview with the AFP news agency.
"The government is doing nothing for us."
Rescue workers have rushed to evacuate thousands of families from the southern part of Sindh province, where floodwaters could burst the banks of the Indus river.
Food prices are expected to rise as the waters continue to swamp agricultural areas.
Pakistan's Express-Tribune newspaper reported "skyrocketing" fruit and vegetable prices on Sunday.
timeline
July 22: Floods first hit the western province of Balochistan, killing dozens.
July 27: Rains move north to Khyber Pakhtunkhwa; death toll tops 1,000.
August 2: Waters hit Punjab, submerging homes and farms.
August 6: Floods move south again, towards Sindh province.
"Floods and rains have made these things unaffordable," one shopper in Lahore told the newspaper.
Millions of acres of crops have been destroyed in Punjab province, often called the "rice bowl" of Pakistan, and across the northwest.
The flooding has also caused extensive damage to Pakistan's electrical infrastructure, forcing power plants to shut down across the country.
Pakistan already suffers from a crippling electricity crisis, with hours-long blackouts a daily occurrence.
More than 252,000 homes have been damaged or destroyed across Pakistan, according to the government.
Pakistan's military said over the weekend that it has rescued more than 100,000 people from flooded areas.
'Zardari's Katrina'
Asif Ali Zardari, Pakistan's president, is expected to return to the country on Monday or Tuesday after a visit to France and the United Kingdom.
FLOOD STATISTICS
1,600 killed
Four million left homeless
15 million displaced or affected
558,000 hectares of farmland underwater
The trip, at the height of the disaster, was criticised by many Pakistanis, who accused Zardari of mismanaging the crisis.
Fatima Bhutto, Zardari's estranged niece, called the flooding "Zardari's Katrina", a reference to George Bush's, the former US president, handling of Hurricane Katrina in 2005.
Many villagers have complained about a lack of basic services in relief camps established by the government and the Pakistani army.
The army has about 300,000 troops working on the relief effort, but some human rights activists are concerned that the military is undermining civilian institutions.
"Yes, it is the military's job to take care of the rescue, but the civil administration must be strengthened and properly organised," Hina Jilani, a Pakistani supreme court advocate, told Al Jazeera.
Jilani said that local communities need to play a larger role in the response.
