Stock markets are on course for another day of heavy losses as concerns mount the coronavirus crisis will lock down global economic activity for an extended time.
US futures tumbled while Asian and European markets went into a sharp reverse gear, with the FTSE 100 hitting levels not seen since June 2012, after Donald Trump announced a 30-day ban on flights to the country from most of Europe, excluding the UK, to help control the spread of COVID-19.
Market analysts said the latest declines, which also followed the official declaration of a pandemic by the World Health Organisation, marked a new front in the rush for safe havens of recent weeks.
Trump's new anti-coronavirus measures
Khoon Goh, head of Asia research at ANZ in Singapore, commented: "The travel ban from Europe has definitely taken everyone by surprise.
"Already we know the economic impact is significant, and with this additional measure on top it's just going to multiply the impact across businesses. This is something that markets had not factored in...it's a huge near-term economic cost."
A lack of detail on promised US government help, including tax breaks, was partly blamed for the Dow Jones Industrial Average entering so-called bear market territory on Wednesday - that is 20% below its peak within just a matter of weeks.
It lost almost 6% on the day and was seen falling a further 5% on Thursday.
Asia took the lead from Wall Street with the Nikkei in Japan and Hong Kong's Hang Seng both tumbling by around the 4% mark.
Germany's DAX and the CAC in Paris were almost 7% down in early deals in a bloodbath for values in Europe - with Norway revealing it could even close airports down to help get a tighter grip on infection rates.
Airline and travel stocks on the FTSE 100 in London built on earlier losses as the index fell by 6.7% at one stage - taking values to 5482 points - a level not seen since June 2012 during the eurozone debt crisis.
Its value has taken a pounding of 28% since January.
BA owner IAG was among the biggest losers, off more than 10%, as the group was seen as.being particularly exposed to the Trump travel ban.
The FTSE had lost 1.4% on Wednesday despite the double-barrelled stimulus announced by the government and Bank of England to support the NHS and wider economy through, possibly, months of disruption ahead.
Coronavirus: Financial system 'part of solution'
Jasper Lawler, head of research at London Capital Group, said: "The biggest source of disappointment on Wall Street was the lack of specific ways to support people and SMEs of the sort that were announced in the UK budget.
"Paid sick leave, free testing and a solution for uninsured Americans were all missing.
"The acrimony between the Republican White House and Democratic Congress since impeachment seems to be making it harder for the US to respond with the speed and vigour required.
"A scheduled one-week recess by Congress starting Friday means further delays to new policy is likely."
A growing number of UK companies, particularly those exposed to the travel sector, have declared themselves unable to forecast full-year revenues and profits as the outbreak evolves.
Among the latest to update the market, WH Smith, said it was expecting a revenue hit of up to £130m because of its exposure to airport shopping.
Intu Properties - behind Manchester's Trafford Centre and Lakeside in Essex - warned of "material uncertainty" over its ability to continue as a going concern after market conditions forced it to abandon capital-raising plans.
The parent firm of foreign exchange service Travelex and Cineworld also issued trading alerts as a result of the crisis - the latter hit by delays to looming blockbuster productions including the latest James Bond movie.
The European Central Bank (ECB) is the latest to come into focus as it is due to announce its latest decision on interest rates at lunchtime on Thursday.
The euro area's main rate is already hovering just above 0% and it is seen as having little more ammunition to burn through given expansive policies already in place to support activity.
Measures to support businesses navigate financial disruption are expected to be announced.