Rocks and boulders tumbled down Mount Kilimanjaro on Wednesday and crashed into a group of climbers sleeping in tents before their final ascent of Africa's highest mountain. Three foreign climbers and an unknown number of guides were killed.

A sudden change in weather at Kibo peak dislodged the rocks, Tanzania National Parks head Gerald Digurube said. He said five foreigners were seriously injured and were taken to Kilimanjaro Medical Center for treatment.

Thomas Kimaro, owner of Alpine Tours, a Tanzanian company that organizes trips to Kilimanjaro, said several Tanzanian guides were among those killed and injured, but he could not say how many.

No information was immediately available on the nationalities or names of the foreign climbers.

Digurube said there were groups organized by several tour operators on the 19,443-foot mountain at the time of the rock slide. The groups had set out for the climb on Saturday.

Kilimanjaro park staff rescued an unspecified number of people who were uninjured, he said.

There were 20-30 foreign climbers at the site at the time of the accident, Kimaro said. They had taken the most difficult and dangerous route to Kibo peak.

"The route needs control, but there are many tourists who seek a challenging ascent and they prefer this route," Kimaro said.

Global warming has melted some of Mount Kilimanjaro's glaciers, Kimaro said, which has loosened rocks once held in place by the ice.