Having already slashed interest rates to below zero and pumped massive amounts of cash into financial markets, it started to directly finance businesses by buying their debt in the bond market.
In the first major trades, the ECB bought millions of euros worth of bonds of French power company Engie and Spain's Telefonica, reported the Bloomberg financial news wire, citing unnamed market players.
Other purchases were of debt issued by brewer Anheuser- Busch InBev, German engineering giant Siemens, Italian insurer Assicurazioni Generali and French automaker Renault, Bloomberg said.
ECB chief Mario Draghi hopes the scheme -- set to be worth billions of euros every month -- will deliver the financial medicine directly where it is needed, with Europe's major public corporations.
The Frankfurt-based bank wants companies to use the extra cash to boost investment, creating jobs and growth in the flagging 19-country currency bloc.
With prices currently falling, the ECB hopes to boost activity and raise inflation back to close to two percent, a level it deems healthy for growth.
Critics however charge that the ECB is overstepping its mandate by lavishing billions on corporate giants and say it could be distorting markets and creating bubbles.
Some also fear that large companies -- which already have access to cheap money thanks to rock-bottom interest rates -- could be tempted to use the extra liquidity for risky merger and take-over gambles.