WASHINGTON (AFP) - President Donald Trump voiced sadness Wednesday after a shooting at a baseball practice in a Washington suburb left a top congressman and several other people wounded.

"We are deeply saddened by this tragedy," Trump said in a statement, adding that he was closely monitoring the developments in Alexandria, Virginia just outside the US capital, where police have arrested the unidentified gunman. 

"Our thoughts and prayers are with the members of Congress, their staffs, Capitol Police, first responders, and all others affected."

Senior Republican Congressman Steve Scalise was among several people shot and wounded during the baseball practice, ahead of an annual game between lawmakers.