Chinese tourists with facial masks stand in front of the New York Stock Exchange (NYSE) on February 3, 2020 at Wall Street in New York City.

Stock markets around the world are tumbling into correction territory as fears of a possible pandemic escalate, with cases of the new coronavirus surging outside China.

More than 83,000 people in around 50 countries have now been infected. World Health Organization Director General Tedros Adhanom Ghebreyesus said on Thursday that the virus has "pandemic potential."

The MSCI ACWI and MSCI World index, both equity benchmarks that track global firms, are both down by around 9% since Monday and are set to mark their worst week since 2008.

In Europe, the Stoxx 600 fell 3.6% to close Thursday's session in correction territory and was down a further 4% on Friday, also heading for its worst week since October 2008.