Four European Central Bank Governing Council members, including Bundesbank chief Jens Weidmann, voted against reactivating the ECB's bond-buying program, central bank sources told Reuters on Friday.

In addition to Weidmann, Executive Board member Juergen Stark and two policymakers from Benelux countries voted against purchasing bonds, the sources said. The ECB began buying bonds again on Thursday after 18 weeks of inactivity.