The European Central Bank on Wednesday unexpectedly said it would spend 750 billion euros (£709bn) on "emergency" bond purchases, as it joined other central banks in stepping up efforts to contain the economic damage from the coronavirus.

The so-called Pandemic Emergency Purchase Programme comes just six days after the ECB unveiled a big-bank stimulus package that failed to calm nervous markets, piling pressure on the bank to open the financial floodgates.

The $820-billion scheme to buy additional government and corporate bonds will only be concluded once the bank "judges that the coronavirus Covid-19 crisis phase is over, but in any case not before the end of the year," the ECB said in statement.

The decision came after the bank's 25-member governing council held emergency talks by phone late into the evening, following criticism the bank wasn't doing enough to shore up the eurozone economy.

ECB chief Christine Lagarde said "extraordinary times require extraordinary action".