The UN Children's Fund (Unicef) said that shelter, safe drinking water, food, warm clothing, and emergency medical assistance were most urgently needed.
It said that clean water was a "priority", adding that children were especially vulnerable to diseases such as diarrhoea and cholera.
Ayub Kakar, the district health officer in Ziarat, a devastated hill town, said: "Due to the cold hundreds of children are being treated for pneumonia, abdominal diseases, diarrhoea and chest problems.
"We fear the death toll will rise. Such diseases, if not treated in time, are life-threatening."
Pakistani authorities have distributed thousands of tents, blankets, coats and food packages, but some highly remote valleys in the mountainous region are still without any shelter.
Many of those seriously injured have been taken to Quetta, the regional capital, but supplies there were low.
Zainullah Kakar, at the city's Bolan Medical College, said it had taken in 90 trauma patients.
"We are running short of antibiotics and other drugs. We need artificial limbs. We need metal plates and rods to treat broken arms and legs,'' he said.
The need for substantial shelters is heightened by the coming winter and subsequent snow.
In Khanozai, near Ziarat, residents were reported to have blocked the main road in protest at the lack of aid despite government pledges to help them.
Mohammad Khan, the owner of an apple orchard, said: "Our children are dying, help us."
In another village, Ahmadoon, people said they were making tents from scavenged clothing.
"Our children could not sleep during the night because of the cold and continued tremors shaking the mountains," Allah Noor, a teacher from Ahmadoon, said.
"People do not go to their damaged houses even to take out food because they fear more tremors."
Major General Mohammed Khan said military and paramilitary troops had provided more than 2,000 tents and 15 tonnes of food rations. He said that more would arrive in the next few days, but warned that reconstruction could take months.
"It is a complete emergency here. Nobody has anything to eat and drink," Dilawar Kakar, the mayor of Ziarat, said.
"We need a lot of resources to reconstruct, and stabilise these trauma stricken people."
Islamist political parties, including Jamaat-ud-Dawa, listed by the US as a "terrorist organisation", have been providing some food, medicine and shelter in some remote areas.
Abu Abdullah, a Jamaat-ud-Dawa volunteer, said that their assistance was not politically charged.
"We believe in serving people," he said. "We are not doing any politics here and we are making every effort to provide relief to the survivors."
The UN World Food Programme pledged to supply emergency rations to those displaced by the disaster for two months, while the International Committee of the Red Cross was distributing some 2,500 tents.
In the capital Islamabad, Farooq Ahmad Khan, chairman of the National Disaster Management Authority, said Pakistan had not issued an appeal for foreign assistance, but any help would be accepted.
'Gripped by fear'
Al Jazeera's Imran Khan, reporting from the Pakistani city of Quetta, said: "This is is a city gripped by fear and perhaps its citizens have a every right to be [afraid].
The last earthquake here was in 1935, and it killed 30,000 people. It is commemorated in Baluchi folklore and memorials.
"This latest earthquake has triggered fears of a mass devasation and some residents of the city have deiciced that it is safer despite the bitter cold to sleep outisde than [it is] to sleep inside."
Meanwhile, the Pakistan Meteorological Department said it had recorded more than 250 aftershocks.
They also said that more are likely to be felt into next week but of decreasing magnitude.