Two children have died and hundreds more have been affected as the Himalayan winter sweeps in.
The UN begged the international community for additional help on Tuesday as it raced against time to save millions of people threatened by disease and hypothermia because of the sudden change in the weather.
More snow fell in mountain villages overnight and temperatures fell below freezing throughout the disaster zone, threatening to bring about a second wave of deaths that aid agencies have warned of.
"Pneumonia has spread among children, according to data received from different places," Sardar Mahmood Khan, district health officer in Muzaffarabad, the ruined capital of Pakistani-administered Kashmir, said on Tuesday.
"We are receiving hundreds of cases in different areas. The winter is severe this year. There is no proper shelter, no clothing for children and no nutrition," Khan said.
Homeless in winter
The 8 October quake killed more than 74,000 people in Pakistan and India, but there are fears they could only be the first wave of deaths as 3.5 million survivors were left homeless.
The UN said late on Monday that two children - a three-month-old boy and a young girl - had died of suspected pneumonia after the first snowfall of the winter in northern Pakistan and Kashmir at the weekend.
"We are receiving hundreds of cases in different areas. The winter is severe this year. There is no proper shelter, no clothing for children and no nutrition"
Sardar Mahmood Khan,
District health officer in Muzaffarabad
"We need ongoing and additional support in the next few days so we could reach as many of the remaining vulnerable people as possible," Andrew MacLeod, the UN emergency operations chief in Pakistan, said in a statement.
He said that most of the $5.8 billion pledged by donors at a conference on 19 November was for long-term rebuilding, while a $550 million UN appeal for immediate aid remains less than half-funded.
"Winter and nature are reminding us: Concentrate on relief in order to save lives, reconstruct later," MacLeod said.
The young girl died from suspected pneumonia on Monday as her father carried her from the remote village of Kumi in northwestern Pakistan to the destroyed town of Balakot 20km away, MacLeod said.
The boy died of pneumonia on the same day after he was brought to a hospital in Muzaffarabad from the nearby Neelum Valley, MacLeod added.
The UN said snow and rain had "severely hampered" its helicopter and truck relief operations.
Two children are thought to have
been killed by pneumonia
International and Pakistani helicopters were flying again on Tuesday after they were grounded throughout Sunday and on Monday morning, said Major Farooq Nasir, the Pakistani army's relief operations spokesman in Muzaffarabad.
Heavy rains lashed the city briefly in the afternoon and isolated snow showers were set to continue in the most mountainous parts of the quake zone until Tuesday evening, the Pakistani meteorological department said.
The weather was expected to be drier on Wednesday morning but a cold wave is on its way, during which daytime temperatures would be less than normal and temperatures at night would plummet below freezing, the weather agency said on its website.
Meanwhile, a series of mild aftershocks jolted northern Pakistan early on Tuesday, but there were no reports of casualties or damage.
A tremor measuring 4.1 on the Richter scale was felt at 4.50am (2350 GMT), one of eight aftershocks recorded in the past 24 hours, chief of the seismological department Qamaruz Zaman said.