Britain is expected pump more than 100 billion pounds ($155.43 billion) into its banking system as it looks to improve the amount of credit being fed through to the real economy, according to the governor of the Bank of England.

Meanwhile, the Bank of Japan kept monetary policy steady but pledged to do its utmost to ensure the country's banking system remains stable if a Greek election this weekend ignites fresh global market turmoil.

European shares closed higher . Spanish and Italian government bond yields eased, while the euro held firm against the U.S. dollar.

Brent crude futures rose near $98 a barrel , extending gains after producer group OPEC agreed to keep its output target unchanged for the second half of the year.

Facebook is expected to file a motion to consolidate all shareholder lawsuits against the company following the botched IPO last month, according to sources. The social-networking giant's lead underwriters, Morgan Stanley, Goldman Sachs and JPMorgan Chase, are expected to join the motion. Facebook soared to close above $30 a share.

On the M&A front, business-software company Yammer agreed to a takeover bid from Microsoft for $1.2 billion, according to reports.