The UN has stopped aid flights to some earthquake survivors in Pakistan administered Kashmir after dozens of people stormed two of its helicopters.
Helicopter supplies are still vital in the quake zone
The people had been demanding evacuation to nearby cities.
Deputy humanitarian coordinator Larry Hollingworth told the BBC that flights into the Lipa Valley area would be suspended to ensure the crews' safety.
He said it was unfortunate that the actions of a minority would deprive the majority of food.
The UN said the survivors had been stranded in mountains and called the incidents extremely disturbing.
There were two incidents, involving more than 50 people. The survivors fled on arriving at Muzaffarabad and Abbottabad. No-one was arrested.
The 8 October quake killed more than 73,000 people and displaced millions.
Since then the UN and dozens of other organisations have remained involved in the emergency relief work.
However, heavy rain and snowfall early this week created new landslides, leaving thousands of people stranded in mountainous regions.
The UN refugee agency says winter has come late to Pakistan but with a vengeance, with temperatures falling to -13 Celsius in the highest villages.
Mr Hollingworth said the two helicopter incidents were regrettable, adding that in both cases the people were transported to safer places and no-one was detained.
The BBC's Zaffar Abbas in Islamabad says these are thought to be the first such incidents since the earthquake.
A senior UN official told the BBC that in one case about 20 people forced their way onto a UN helicopter as it was about to leave the town of Banamula, after dropping food supplies.
He said some of the people were rowdy and misbehaved with the UN staff. Eventually the helicopter crew had no choice but to fly them to Muzaffarabad.
In the second case, about 35 people stormed a UN helicopter and had to be evacuated to the town of Abbottabad, although it was not clear where the incident started.
Mr Hollingworth said the UN was in touch with the Pakistani military and civilian authorities and the matter was being investigated.
"I presume they were coming down from the mountains and basically wanted out. It's very cold there," Mr Hollingworth said.
Pilots of other flights to the high-altitude areas have been returning with letters from people there begging to be evacuted.
The relief effort is still a huge operation, with helicopters vital in transporting supplies.
The UN refugee agency, UNHCR, says that either because of adequate supplies or blocked roads there has been no mass migration yet from upper valleys.
However, it says it is prepared to receive 50,000 more people in camps if necessary.