(Bloomberg) - Mr Zhou Xiaochuan, governor of China's central bank, could not stop repeating to a G-20 gathering that a bubble in his country had "burst".

It came up about three times in his explanation on Friday (Sept 4) of what is going on with China's stock market, according to a Japanese Finance Ministry official.

When asked by a reporter if Mr Zhou was talking about a bubble, Japanese Finance Minister Taro Aso was unequivocal: "What else bursts?"

A dissection of the slowdown of the world's second-largest economy and talk about the equity rout which erased $5 trillion (S$7.1 trillion) of value was a focal point at the meeting of global policymakers in Ankara. That was not enough for Mr Aso, who said that the discussions had not been constructive.

Chinese stocks have plunged almost 40 per cent since a June peak, triggering unprecedented intervention from the authorities. The central bank in August cut rates for the fifth time since November and lowered the amount of cash banks must set aside, falling back on its major levers to support equity prices and the slowing economy.

It was China, rather than the timing of an interest-rate increase by the US Federal Reserve, that dominated the discussion, according to the Japanese official, with many people commenting that China's sluggish economic performance is a risk to the global economy and especially to emerging-market nations.

"It's clear there are problems in the Chinese market, and at today's G-20 meeting, many people other than myself also expressed that opinion," Mr Aso said after a meeting of finance chiefs and central bank governors.

The PBOC shocked global markets by allowing the biggest yuan depreciation in two decades on Aug 11, when it changed the exchange-rate mechanism to give markets a bigger role in setting the currency's level.

That historic move would not get a mention in the communique, according to the Japanese official, who asked not to be named, citing ministry policy.