At least 87 people were killed and more than 180 injured when a crane crashed through the ceiling of the Grand Mosque of Mecca amid high winds and thunderstorms today.
Dramatic footage shows the moment the crane toppled in heavy rain, with another video capturing the chaos and confusion inside the building as people run for cover after the impact.
Photos posted on social media shows the polished tiled floor of the mosque covered in rubble, bodies and pools of blood, and people fleeing the area bleeding and covered in soot.
The tragic incident in Saudi Arabia occurred shortly before the 6:30pm Friday evening prayer session - one of the busiest times of the week - causing devastation to what is the largest mosque in the world.
Hundreds of thousands of Muslims are gathering at the holy site from all over the world for the annual hajj pilgrimage set to begin later this month.
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Thunderstorms: A picture captures the moment the fatal crane was struck by lightning prior to collapsing into the mosque, killing dozens
Disaster: The Grand Mosque is usually at its most crowded on Fridays, the Muslim weekly day of prayer
A massive project is currently under way to increase the area of the mosque by 4.3million sq ft - so that it can accommodate up to 2.2 million people at once.
The crane belongs to a German crane company operated by the Bin Laden family's consortium, who are heading the expansion of the Holy Mosque.
Saudi BinLaden Group was founded by Osama's Bin Laden's billionaire father Mohammed and the sprawling construction conglomerate runs a large amount of major building contracts in the Sunni kingdom.
Pictures taken before the disaster show the crane being struck by a bolt of lightning and authorities are in little doubt extreme weather was to blam
Earlier, the Civil Defense had issued thunderstorm, heavy rain and wind warnings in the area and authorities say search and rescue teams and medical workers from the Saudi Red Crescent are now at the scene.
The Grand Mosque, or Great Mosque of Mecca, surrounds Islam's holiest place, the Kaaba, in the city of Mecca.
The mosque is usually at its most crowded on Fridays as it is the Muslim weekly day of prayer, when Muslims face in the direction of the Kaaba while performing their obligatory daily prayers.
One of the five pillars of Islam requires every Muslim to perform the Hajj pilgrimage at least once in their lifetime.
Muslim faithful from about 160 countries converge on the Islamic city and other locations in western Saudi Arabia to complete the holy journey.
Heavy death toll: At least 87 people were killed and more than 150 were injured in today's accident in Saudi Arabia's holy city
Struck before evening prayers: Pictures emerging on social media show the scale of casualties with bodies strewn across the mosque floor
Horror: Rescue workers, locals and pilgrims who have journeyed to Mecca watch in horror as victims of the crane accident are laid out
The pilgrimage, one of the largest religious gatherings in the world, has been prone to disasters in the past, mainly from stampedes as pilgrims rushed to complete rituals and return home. Hundreds of pilgrims died in such a stampede in 2006.
Saudi authorities have since lavished vast sums to expand the main haj sites and improve Mecca's transportation system, in an effort to prevent more disasters.
Security services often ring Islam's sacred city with checkpoints and other measures to prevent people arriving for the pilgrimage without authorization.
Those procedures, aimed at reducing crowd pressure which can lead to stampedes, fires and other hazards, have been intensified in recent years as security threats grow throughout the Middle East.
Last year, the kingdom reduced the numbers permitted to perform haj for safety reasons because of construction work to enlarge the Grand Mosque.
Al Jazeera's Hasan Patel, reporting from Mecca, said witnesses told him that a crane fell on the third floor of the Grand Mosque around 5.45pm.
Our correspondent said the mosque was packed, even though the incident happened shortly before the 6.30pm prayer.
'Dozens of ambulances are heading to the site. The authorities closed off the area shortly afterwards,' he said.
'This whole place is already a construction site. What made it worse is that around 5.30pm there was severe rain and it's just gushing down the road,' he said.
'I am surrounded by people who are grieving. The mood here is of sadness.'
Al Jazeera's Omar Al Saleh said bad weather was thought to be the cause of the accident - western Saudi Arabia has been hit by strong sand storms in the last few days.
View from the outside: The toppled crane leans on the Mosque, with the top section of the vehicle having crashed through the ceiling
Fighting for his life: An injures man lies out on a makeshift stretcher, covered in blankets, while others hold his drip
Holy site: The Great Mosque houses the Kaaba - the massive cube-shaped structure towards which Muslims worldwide pray
Weather warnings: Before today's accident, the country's Civil Defense had issued thunderstorm, heavy rain and wind warnings in the area
Devastation: The fallen crane lies on its side, leaning on the Grand Mosque as witnesses gather in the holy city of Mecca, Saudi Arabia
Largest mosque in the world: Last year, the kingdom reduced the numbers permitted to perform haj for safety reasons because of construction work to enlarge the Grand Mosque
Desperate bid to save lives: Ambulances gather in the square outside the Grand Mosque as hundreds of injured of people are carried out
Bodies of victims lie on the ground while injured people are attended to by emergency services
Confusion and anguish: People stand in disbelief and crowd around emergency workers as loved ones are treated
Emergency response: The Saudi Civil Defense says search and rescue teams and medical workers from the Saudi Red Crescent are at the scene
Dozens killed: At least 154 people have been injured in the disaster and at least 65 people are dead
High winds: Extreme weather is believed to have been the cause of the accident, which claimed at least 65 lives this evening
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