At least 107 people died when a massive construction crane crashed into Mecca's Grand Mosque, with scores more injured, Saudi authorities said, days before the annual haj pilgrimage.
SPA said that almost 800,000 pilgrims had arrived by Friday for the haj, which all able-bodied Muslims are expected to perform if they have the means to do so. Last year, just over two million people took part.
Though marred in the past by deadly incidents including floods, stampedes and fires, the haj has become nearly incident-free in recent years because of multi-billion dollar investments.
A massive project is under way to expand the area of the mosque by 400,000 square metres (4.3 million square feet), allowing it to accommodate up to 2.2 million people at once.
Britain's David Cameron also used the micro-blogging site to say: "My thoughts and prayers are with those who have lost loved ones at #mecca today".
Prime Minister Narendra Modi took to Twitter to express his sorrow over the incident. "My thoughts & prayers are with the families of those who lost their lives in the crane crash in Mecca. I wish the injured a quick recovery" he said.
The governor of Mecca region, Prince Khaled al-Faisal, has ordered an investigation into the incident and was heading to the mosque, the official @makkahregion account on Twitter said.
The incident occurred as hundreds of thousands of Muslims from all over the world gather for the annual haj pilgrimage expected to begin on September 21. The Grand Mosque is usually at its most crowded on Fridays, the Muslim weekly day of prayer.
Pictures and videos on social media showed bloodied bodies strewn across a courtyard and people screaming and rushing around right after a massive crash was heard and as fog engulfed the city.
The Kaaba is a massive cube-shaped structure at the centre of the mosque towards which Muslims worldwide pray and which has a major role in the haj.
Abdel Aziz Naqoor, who said he works at the mosque, told he saw the crane fall after being hit by the storm. "If it weren't for Al-Tawaf bridge the injuries and deaths would have been worse," he said, referring to a covered walkway that surrounds
That came about an hour after it tweeted that Mecca was "witnessing medium to heavy rains," and pictures on social media showed lightning. Ahmed bin Mohammad al-Mansoori, spokesman for the two holy mosques, was quoted by the official Saudi Press
The civil defence agency said on Twitter that emergency teams were sent to the scene after a "crane fell at the Grand Mosque," one of Islam's most revered sites.
Massive crane crash at Mecca’s Grand Mosque leaves 107 dead