FRANKFURT (Reuters) - European Central Bank policymakers agreed on a monthly bond purchase target when they met on Thursday but had different views on the desirable level of yields, three sources told Reuters. The ECB said on Thursday it would accelerate bond purchases “significantly” to keep a lid on euro zone borrowing costs but President Christine Lagarde said they did not have a volume goal in mind. The sources said policymakers set on a monthly target for the its Pandemic Emergency Purchase Programme with a small tolerance band around it but agreed not to reveal it. The sources added that buys would not be as high as the 100 billion euros a month the ECB was buying in the spring of 2020 but it would still be well above the 60 billion euros worth of bonds the ECB bought last month. One of the sources said the ECB aimed to push down yields to where they were in December while another said improved economic prospects meant part of the recent increase in yields was justified. An ECB spokesman declined to comment