LONDON — World markets were back in sell-off mode on Tuesday as a 6% slump in Chinese shares following more weak data there and oil’s slide below $30 a barrel again led to a renewed bout of selling.

The plunge in China capped a miserable day for Asia, and European bourses quickly followed suit, with shares in London, Frankfurt and Paris tumbling 1.5% to 1.8% in a bumpy start to trading.

Investors retreated to traditional safe-haven plays, sending the Japanese yen back up against the dollar, gold higher and yields on two-year German government debt to record lows deep in negative territory.

Derek Halpenny, European Head of Global Markets Research at Bank of Tokyo-Mitsubishi, said the drop in Chinese markets was another blow to sentiment, but it was the fresh oil slump that was probably the bigger concern.

"There was a natural question after the rebound last week whether we were seeing a turning point," he said. "But this reversal again is prompting investors to think there is more to come of what we have had in the first three weeks of the year." Brent crude was down another $1.13 at $29.37 a barrel as early European trading gathered momentum, having dropped 5% on Monday. US benchmark WTI fell $1.03 to $29.31, having gone as low as $29.25 overnight.

The chairman of Saudi Aramco, the world’s biggest oil producer, added fuel to the oversupply story that has driven prices down 75% since their 2012 peak.

He said on Monday the firm was continuing to invest in oil and gas production capacity despite other cost-cutting plans.

A senior Iraq oil official said its now record-high output could continue to rise, while Kuwait’s Organisation of the Petroleum Exporting Countries (Opec) governor said the organisation could not make cuts if non-Opec countries were still cranking up their production.

"Psychological factors have driven the severe volatility in the market," said Kang Yoo-jin, a commodities analyst at NH Investment and Securities based in Seoul, Korea, who added the situation was likely to persist until concerns over oversupply eased.

Asia’s turbulent session saw mainland Chinese shares slump more than 6% to a 14-month low in another sign that authorities in Beijing had their work cut out for them in their efforts to stabilise the fickle domestic markets.

There was more gloomy data, too, as China’s annual rail freight volume, viewed as a good temperature gauge of the giant economy, fell 11.9% last year versus a drop of 3.9% in 2014.

The region’s heavyweight indexes, Japan’s Nikkei and Hong Kong’s Hang Seng Index fell 2.4% and 2.5% respectively too, as the first two-day run of gains of the year came to a shuddering halt.

"Wherever you look — China, oil and the US, there is no clear evidence of improvement in economic fundamentals," said Tatsushi Maeno, MD at PineBridge Investments. "So in the near term, it is hard to expect risk asset prices to gain further." The big currency market moves were inevitably in the emerging market heavily linked to oil.

A 2.4% drop sent Russia’s rouble back towards its recent record low, while the rand, Turkish lira and most Asian units also drooped against the dollar.

Among the majors, the dollar was making way as it fell against the low-yielding yen and euro. There was some extra caution on the dollar ahead of the start of the first two-day meeting of the year of the Federal Reserve.

Investors will comb the US central bank’s message to determine what, if any, effect volatile global markets, plummeting oil prices and fears of a Chinese slowdown will have on its previously stated intentions to keep raising rates this year.

US interest rate futures implied that traders put the chance of a Fed rate hike this week at just 13%. Over the year, markets are now pricing in only one hike, compared with the Fed’s rate path, which factors in at least four rises.

"There is a fair bit of nervousness going into the Fed meeting. Interest rate markets have postponed rate hikes in 2016 and 2017 so investors expect something dovish from the Fed, given the volatility in stock markets," said Niels Christensen, FX strategist at Nordea.