The European Central Bank on Wednesday announced a surprise €750 billion scheme to purchase government and corporate bonds.
It comes as it joined other central banks in stepping up efforts to contain the economic damage from the coronavirus.
The '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 asset purchasing scheme will be temporary and 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", it said in statement.
The decision came after the bank's 25-member governing council held emergency talks by phone late into the evening.
The ECB said it was "committed to playing its role in supporting all citizens of the euro area through this extremely challenging time".
"The governing council will do everything necessary within its mandate," it said, adding that the size of the asset purchases could be increased if needed.
It also said it stood ready to relax some self-imposed restrictions on bond purchases to potentially help countries like Italy whose bond yields have soared over the coronavirus panic.
Critics had in recent days slammed the ECB for not doing enough to support the euro zone compared to the drastic action taken by the US Federal Reserve.
But the immediate reaction from analysts was positive.
The ECB's latest medicine could be "a game changer for the euro area economy and credit markets" if it was accompanied by fiscal action from eurozone governments, Pictet Wealth Management strategist Frederik Ducrozet said.
ECB President Christine Lagarde said the bank intends to use all tools to defend the euro as "there are no limits" to its commitment to the single currency.
"Extraordinary times require extraordinary action," Ms Lagarde tweeted.