FBI probes gunman's motive in 'ambush' shooting of Guardsmen near White House

Trump calls for Afghan refugees to be investigated after shooting

Streets are blocked after reports that two National Guard soldiers were shot near the White House in Washington. Picture: Anthony Peltier/AP.

Investigators led by the FBI's joint terrorism task force sought clues on Thursday to what drove an Afghan immigrant to open fire on two National Guard soldiers mere blocks from the White House in what officials called an "ambush" attack on Thanksgiving eve.

The two soldiers, part of a militarized law enforcement mission ordered by US President Donald Trump months ago and challenged in court by officials of the District of Columbia, were hospitalized in critical condition.