A Pakistani teacher has described how he saved his wife from a deadly stampede in Saudi Arabia by pulling her from her wheelchair as fellow haj pilgrims were trampled to death around them.

At least 769 people died in a crush of pilgrims near Mecca on Thursday when two large groups converged at a crossroads, in the worst disaster to befall the annual event in a quarter of a century.

Alamzeb Khan, 48, and his wife, who was suffering from a high fever, were almost killed when the crowd panicked.

The stampede at Mina, where the couple had gone to throw stones at three pillars representing the devil, part of the haj ritual, looked like the "day of judgment," he said.

"To save their lives, some pilgrims trampled other pilgrims as if they were not human," he said.

The crush began when two groups of pilgrims, some from Iran and some from Africa, crashed into each other, he said.

"The elderly, women and sick pilgrims were the first to fall. They fell and were trampled by others," he said. Khan fell too and injured his arm, but he battled against the crowd to grab his terrified wife's hands. The wheelchair had saved her from being pushed over, he said.

"I feared she had been crushed by the pilgrims, but luckily she survived. I immediately grabbed her out of the wheelchair and pushed her to the side. Then we started climbing the steel fence to save our lives," he recalled.