The European Central Bank (ECB) Vice President Vitor Constancio said in a speech on Monday that the central bank's stimulus measures needed more time to take effect.

"We have to allow some time for the package of measures adopted in March to produce its effects, while closely monitoring external developments," he said.

Constancio pointed out that the ECB was ready to add further stimulus measures to reach 2% inflation target.

"The ECB will continue to do what is necessary to achieve its goal of reaching a level of inflation close to 2% and enough policy tools can still be used," the ECB vice president said.