Tens of thousands of pro-democracy protesters are blocking Hong Kong's streets, shutting down its business hub amid a row about how the city's leader should be elected.

Elections are due in 2017 - but the Chinese government has issued a ruling limiting who can stand as a candidate, which has angered activists who want full democracy.

The demonstrations have spread to other areas including a shopping district and a residential area, and China has warned other countries not to support what it calls "illegal rallies".

BBC News explains the row - in 60 seconds.

Video produced by Helier Cheung and Paul Harris

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