Kashmiri woman comforts an elderly woman who lost her daughter by Saturday's heavy earhquake in Muzaffarabad

Donor nations are rushing doctors, helicopters, food and tents to quake-devastated Pakistan, where the death toll from the disaster has surpassed 20,000.

In the worst hit city, Muzaffarabad, shopkeepers clashed with looters, while hungry families huddled under make-shift tents waiting for relief.

Aid agencies say more than 120,000 people are in urgent need of shelter and up to four million could be left homeless by the 7.6 magnitude earthquake which caused destruction throughout Pakistan's northern mountains.

South Asia's strongest in 100 years, the quake also killed more than 900 people in India.

U.N. Secretary-General Kofi Annan says he had instructed all parts of the U.N. system to do everything possible to help.

The International Red Cross says it aims to provide emergency food and shelter to more than 100,000 vulnerable people stranded in freezing weather.

More flights carrying rescuers and aid are expected from the United States, Iran, Russia and other countries.