Saudi unveils world's largest clock

A giant clock on a skyscraper in Islam's holiest city Mecca began ticking on Wednesday at the start of the fasting month of Ramadan, amid hopes by Saudi Arabia it will become the Muslim world's official timekeeper.

The Mecca Clock, which Riyadh says is the world's largest, has four faces measuring 43 metres in diameter.

It sits 400 metres up what will be the world's second-tallest skyscraper and largest hotel, overlooking the city's Holy Grand Mosque, which Muslims around the world turn to five times a day for prayer.