Hong Kong: Chinese markets were suspended Thursday for the second day this week after they fell more than seven per cent, leading an Asia-wide sell-off as Beijing weakened the value of the yuan currency by the most since August.

In a painful echo of the summer rout that wiped trillions of dollars off valuations, mainland investors sold up on fears about the world's number two economy, a key driver of global growth.

The losses mark one of the worst starts to a trading year for decades as nerves are shedded by a perfect storm of weak global growth - particularly in China - a slump in oil prices to more than 11-year lows and geopolitical tensions.

Regulators in China called an end to trade within just 30 minutes of opening after the central bank weakened the value of its yuan currency by 0.51 per cent against the dollar.

The drop was the biggest since August when the value was cut by five percent in a week - sparking weeks of global market turmoil over worries Beijing did not have a handle on its economic crisis. The yuan is now at its weakest in five years.

"The Chinese yuan is smack bang at the heart of concerns. For risk assets to stabilise and sentiment to turn around, we are going to need a stable or even positive move in the Chinese currency," Chris Weston, chief market strategist in Melbourne at IG Ltd, told clients, according to Bloomberg News.

Trading was halted just before 10am (0200 GMT) as a "circuit breaker" kicked in after the benchmark Shanghai index slumped seven percent and the Shenzhen composite index, which tracks stocks on China's second exchange, tumbled 8.2 percent.

The stop - activated when markets fall more than seven per cent - was also triggered on its first day Monday.

It is based on the CSI 300 index, which tracks the largest 300 stocks on the two exchanges.