U.S. stocks tumbled at the open on Thursday as global shares also declined after Federal Reserve Chairman Ben Bernanke hinted the central bank may scale back its bond-buying program later this year.

In a press conference after the Fed's policy statement on Wednesday, Bernanke said that if the economy continues to improve, quantitative easing could start winding down towards the end of 2013, and end in 2014.

Wall Street declined also on jobless claims data that revealed the number of Americans filing new claims for unemployment benefits rose more than expected last week.  Jobless claims jumped 18,000 to a seasonally adjusted 354,000 last week, according to the Labor Department. 

Separate data showed the HSBC China Purchasing Manager's Index (PMI) fell to a nine-month low of 48.3, compared to the final reading of 49.2 in May. 

Existing-home sales rose in May to the highest pace since November 2009, as sales rose 4.2 percent in May to a seasonally adjusted annual rate of 5.18 million, the National Association of Realtors reported Thursday. 

The U.S. June flash factory PMI was little changed as the index inched lower to a 52.2 reading in June from 52.3 in May, Markit said Thursday.