FRANKFURT — Just weeks ago, the European Central Bank began a bond-buying program intended to stimulate the economy and to last at least 18 months. On Wednesday, the bank’s president, Mario Draghi, indicated that the measure had already begun to bear fruit.

The eurozone as he described it is benefiting from a convergence of low oil prices, improved government policy and — not least — the bank’s newest stimulus program.

A bond-buying program begun a month ago is “proceeding smoothly,” Mr. Draghi said at a news conference, which happened to take place on one of the balmiest spring days of the year so far in Frankfurt.

Mr. Draghi’s news conference did not proceed quite as smoothly. As he was briefing reporters, a young woman jumped from the news media seats, tossed papers and confetti at Mr. Draghi and shouted “end E.C.B. dictatorship” before she was subdued by security guards. It was a rare breach of bank security.