Cyber attacks on U.S. government agency Web sites, including that of the White House, are continuing on Thursday.

State Department spokesman Ian Kelly told reporters Thursday that the attack on the department’s Web site that started on Sunday is still ongoing, but has currently reduced.

Kelly said other U.S. government agencies were exposed to the recent attacks, adding that a computer emergency countermeasure team is working with related agencies to combat the so-called “distributed denial-of-service” attacks that attempt to paralyze sites by flooding them with huge amounts of data.

A dozen U.S. government sites have come under attack --- including those of the White House, Defense Department and State Department --- while the New York Stock Exchange was among private sector sites that were hit in recent days.

The U.S. government has reportedly blocked attempts from South Korea to access state and defense department sites in a bid to prevent further damage.