The European Central Bank dismissed speculation of an early end to its ultra-easy money policy at a protest-marred press conference on Wednesday, saying its medicine is already fuelling economic recovery.

The ECB's governing council, meeting a day earlier than usual because of weekend meetings of the World Bank and International Monetary Fund, voted to hold its key interest rates at their current all-time lows.

The traditionally staid post-meeting news conference was briefly interrupted when a young woman charged at ECB chief Mario Draghi calling for an "end to the ECB dictatorship".

The woman, wearing a T-shirt with the same slogan but spelled "dick tatorship", jumped onto the podium where Draghi was seated and scattered confetti on him.

She was quickly apprehended and escorted out of the premises before the news conference resumed.

Police told AFP afterwards that the 21-year-old woman from Hamburg had had a valid media accreditation. She was questioned by police but later released, a Frankfurt police spokesman said.

The ECB has frequently been the target of protests, but this was the first time a demonstrator has actually infiltrated the building, where security is normally extremely tight.

Last month, dozens of people were injured when violent clashes between anti-capitalist protesters left a trail of destruction at the official inauguration of the ECB's new headquarters in the east of Germany's financial capital.

- QE is working -

Resuming the news conference, Draghi said there was "clear evidence" that the ECB's raft of different monetary policy measures -- including the contested policy of quantitative easing or "QE" -- were proving "effective".

"Financial market conditions and the cost of external finance for the private sector have eased considerably over the past months and borrowing conditions for firms and households have improved notably, with a pick-up in the demand for credit," he said.

"Looking ahead, our focus will be on the full implementation of our monetary policy measures."

Quantitative easing or QE is a massive 1.1-trillion-euro ($1.2 trillion) sovereign bond purchase scheme aimed at bringing area-wide inflation back up to levels consistent with healthy economic growth.

Under the programme, the ECB aims to buy 60 billion euros of bonds per month until September 2016.

The scheme has its critics, not least the head of the German central bank or Bundesbank, Jens Weidmann, who fear it will lessen pressure on governments to get their economies and finances in order.

- Marathon run -

Opponents are likely to argue for an early roll-back of the programme as the eurozone recovery picks up speed.

Draghi said he was surprised that already markets were speculating about a possible phasing out of QE.

"I'm quite surprised frankly by the attention a possible early exit of the programme is receiving, when we've been in the programme only a month," Draghi said.

It would be like a long-distance runner asking when a marathon might be over after the first kilometre, he said.

And he insisted that the programme would last at least until September 2016 "and, in any case, until we see a sustained adjustment in the path of inflation that is consistent with our aim of achieving inflation rates below, but close to, 2.0 percent over the medium term," the ECB chief said.

Tom Rogers of EY Eurozone Forecast said that "the fact that the most dramatic thing about today's ECB press conference was the intervention of a protester is a sign of just how much the outlook for the eurozone economy has improved in the past six months or so".

"All in all, Draghi clearly tried to temper any taper discussion. Whether he will succeed is uncertain," said ING DiBa economist Carsten Brzeski.

Craig Erlem, analyst at Oanda, said: "You know it's been a dull press conference when the only real talking point to come from it is a protestor jumping on the table in front of Mario Draghi, throwing confetti on him. That was very much the case today.

"All things considered, as expected, today was something of a non-event from the ECB."