At least 65 people have died after a crane collapsed on the Grand Mosque in the Muslim holy city of Mecca, Saudi Arabia's civil defence authority has said.
About 154 people were injured, the civil defence authority tweeted.
It is not known what caused the accident, but images from the scene showed part of a huge red crane had crashed through the mosque roof.
Mecca is preparing for the annual Muslim Hajj pilgrimage.
Hundreds of thousands of people are expected to arrive in the Saudi city from all over the world later this month.
Saudi authorities began a major expansion of the site last year to cope with ever-growing numbers of worshippers.
The crane that collapsed on Friday was part of the construction work taking place at the site.
Strong winds have lashed the Arabian peninsula in the past week.
The Grand Mosque
The Masjid al-Haram, or Grand Mosque, in the Saudi city of Mecca is Islam's most sacred site and the destination for millions of Muslims undertaking the Hajj pilgrimage every year.
At the heart of the mosque, the oldest parts of which date to the 16th century, is the Kaaba, a black cube-shaped building which Muslims all over the world face when they pray.
Islam requires that every Muslim capable of doing so performs a pilgrimage to the site at least once in their lifetime. Once at the mosque, pilgrims perform Tawaf - walking seven times around the Kaaba in a counter-clockwise direction.