Doctors in quake-stricken areas of Pakistan have begun a campaign to immunize 800,000 children against potentially killer diseases before the bitter Himalayan winter.

U.N. health officials said Sunday that teams with vaccines for measles, diphtheria, polio and other illnesses fanned out to remote communities in helicopters from the city of Muzaffarabad in Pakistani-controlled Kashmir.

The officials said they hope to reach all the quake-stricken areas within a two-week window of opportunity before the weather turns severe.

One official said that children living in remote mountain villages, cut off by landslides, were particularly vulnerable due to malnutrition.

International organizations say last month's 7.6 magnitude earthquake killed at least 86,000 Pakistanis and made some three million homeless. More than 1,300 people were killed in Indian Kashmir.

Some information for this report provided by Reuters and AP.