Some activists accuse the ECB of enforcing budget austerity measures on eurozone countries, such as Greece, that are under financial bailout programmes.
Mr Draghi reappeared on stage a few minutes later and carried on with his remarks.
He said the ECB intends to pursue its existing bond-buying stimulus programme "until the end of September 2016 and, in any case, until we see a sustained adjustment in the path of inflation". Inflation at minus 0.1% is way below the ECB's aim of 2%.
There was some speculation that because of a recent improvement in the economy of the 19-country eurozone, the ECB might end its stimulus programme before that date.
In his statement, Mr Draghi noted that the ECB would look beyond month-by-month swings in economic data when assessing how long to carry on with the stimulus.
The stimulus hopes to lower market interest rates, which tends to boost lending and, by extension, economic activity. The US Federal Reserve has used a similar programme.
Mr Draghi said the stimulus programme is proceeding smoothly and has helped lower market interest rates.
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