By Agence France-Presse
Wall Street attempted a rally following favorable US inflation numbers but it fizzled as markets were easily upset by a string of worrisome reports.
Analysts continued to downgrade Apple, a bellwether stock for the tech sector, on fears of weak demand for iPhones.
Meanwhile in Washington, a senior Democratic legislator warned the days of soft-touch oversight of financial regulators were coming to an end -- helping drive major bank shares into the red.
Negative economic data from Japan and Germany and turmoil surrounding the conclusion of Brexit talks added to volatility.
All three major US indices hit their lowest levels since late October, with the benchmark Dow Jones Industrial Average down for the fourth straight day -- its longest losing streak since August.
"What is really bothering the market is the worry we are in the late stages of the economy's growth and that you are doing that at a time when international growth is slowing," Karl Haeling of LBBW told AFP.
Worries about what Trump will do next in the US-China trade war also dampened investor appetite, he added.
European equity markets ended a volatile session lower, as the pound sterling gained on hopes of some kind of Brexit deal, dealers said.
The pound had a rollercoaster day as British Prime Minister Theresa May worked to defend her divorce deal with the EU before rowdy lawmakers.
She later won the support of her splintered cabinet, and anticipation of her remarks shortly after markets closed pushed the currency firmly into positive territory.
- 'Hot tin roof' -
"The pound is behaving like a cat on a hot tin roof," said David Lamb, head of dealing at Fexco Corporate Payments, as the British currency flitted between gains and losses over the day.
Eurozone stocks meanwhile suffered from a damaging standoff between Italy and the EU over Rome's budget as well as skepticism surrounding Brexit.
"Uncertainty around Italy and Brexit are weighing on sentiment," said CMC Markets analyst David Madden.
Italy's populist government defied the European Commission by sticking to a big-spending budget plan, risking financial sanctions in a high-stakes standoff that could spell fresh trouble for the eurozone.
Oil prices, meanwhile, clawed back some of the sharp losses this week seen on oversupply fears just as demand falters in the face of the China-US trade war and easing economic growth.
However, prices are still down from their four-year highs seen in early October.
"The dramatic selling across the oil markets in recent days has come to a brief pause," said Jameel Ahmad, head of market research at FXTM, "but many remain stunned by the acceleration in aggressive momentum that has transpired over the past couple of sessions."
Energy giant Russia, which has been cooperating with OPEC on production cuts, said Wednesday it had agreed with the cartel's members to keep a close eye on the oil market at a meeting in Abu Dhabi at the weekend.
"We agreed to monitor the market in November," Russia's Energy Minister Alexander Novak said on the margins of an ASEAN meeting in Singapore.
"We have the necessary tools to deal with any signs of a serious crisis," he said, according to the RIA news agency.
Key figures around 2200 GMT
New York - Dow: DOWN 0.8 percent at 25,080.50 (close)
New York - S&P: DOWN 0.8 percent at 2,701.58 (close)
New York - Nasdaq: DOWN 0.9 percent 7,136.39 (close)
London - FTSE 100: DOWN 0.3 percent at 7,033.79 points (close)
Frankfurt - DAX 30: DOWN 0.5 percent at 11,412.53 (close)
Paris - CAC 40: DOWN 0.7 percent at 5,068.85 (close)
Milan - FTSE MIB: DOWN 0.8 percent at 19,077.47 (close)
EURO STOXX 50: DOWN 0.6 percent at 3,205.36 (close)
Pound/dollar: UP at $1.2989 from $1.2977 late Tuesday
Euro/dollar: UP at $1.1307 from $1.1290
Dollar/yen: DOWN at 113.64 yen from 113.81 yen
Tokyo - Nikkei 225: UP 0.2 percent at 21,846.48 (close)
Hong Kong - Hang Seng: DOWN 0.5 percent at 25,654.43 (close)
Shanghai - Composite: DOWN 0.9 percent at 2,632.24 (close)
Oil - Brent Crude: UP 65 cents at $66.12 per barrel
Oil - West Texas Intermediate: UP 56 cents at $56.25