"If required, we will act swiftly with further monetary policy easing. The Governing Council is unanimous in its commitment to using also unconventional instruments within its mandate should it become necessary to further address risks of too prolonged a period of low inflation," Draghi told a news conference.

He added that "for all practical purposes" interest rates had reached the bottom.

The ECB earlier cut its main interest rate to 0.15 percent and imposed negative interest rates on banks' overnight deposit.

Draghi said it has come to its decision after studying its staff's latest economic forecasts.

(Writing by Eva Taylor Editing by Jeremy Gaunt)