At least 65 people were killed and 80 injured when a construction crane crashed into the Grand Mosque of Saudi Arabia’s holy Muslim city of Mecca Friday, the Saudi civil defense said on Twitter.

At least 65 people were killed and 80 injured when a construction crane crashed into the Grand Mosque of Saudi Arabia's holy Muslim city of Mecca Friday, the Saudi civil defense said on Twitter.

Pictures circulating on social media showed bloodied bodies strewn across a courtyard where the top part of the crane, which appeared to have collapse or snapped, had crashed into it.

It was raining heavily at the time.

The incident occurred as hundreds of thousands of Muslims gather from all over the world for the annual hajj pilgrimage set to begin later this month.

The Grand Mosque is usually at its most crowded on Fridays, the Muslim weekly day of prayer.

A massive project is currently underway to increase the area of the mosque by 400,000 square meters (4.3 million square feet), allowing it to accommodate up to 2.2 million people at once.

The mosque is surrounded by a number of cranes.

The hajj has largely been incident-free during the past few years, with Saudi Arabia investing billions of dollars in transport and other infrastructure to facilitate the movement of the huge numbers of people who take part in Hajj rituals.