At 3pm CET the rate of return to investors on benchmark Spanish ten-year bonds hit a record low of 1.450 percent, down from 1.530 percent the night before.
Meanwhile, the yield on Italian ten-year bonds hit a record of 1.609 percent, down from 1.691 percent on Wednesday.
The ECB announced that it will buy €60 billion of European debt every month from March 2015 until September 2016.
"The combined monthly purchases of public and private sector securities will amount to €60 billion," ECB President Mario Draghi told journalists at a press conference in Frankfurt.
The bond-buying programme will continue "until we see a sustained adjustment in the path of inflation which is consistent with our aim of achieving inflation rates below, but close to, 2 percent," he added.
Spending €60 billion a month for that long would mean the bank injecting over €1.1 trillion into the economy.
The Euro immediately dropped sharply against the US dollar on the news.