A tense exchange erupted between US President Donald Trump and Congresswoman Ilhan Omar on Tuesday as the president criticized Democratic lawmakers over immigration policy and accused them of failing to support border enforcement.

During his State of the Union address before a joint session of Congress, Trump urged lawmakers to stand if they agreed with what he described as a "fundamental principle" of his administration.

"One of the great things about the State of the Union is how it gives Americans the chance to see clearly what their representatives really believe.

"So tonight, I'm inviting every legislator to join with my administration in reaffirming a fundamental principle. If you agree with this statement, then stand up and show your support. The first duty of the American government is to protect American citizens, not Illegal aliens," he said.

Democratic lawmakers remained seated, and Trump responded sharply from the podium.

"You should be ashamed of yourself, not standing up. You should be ashamed of yourself," he said.

The president continued by calling on Congress to end so-called sanctuary city policies and to impose penalties on public officials who block the removal of undocumented immigrants accused of serious crimes.

As Trump spoke, Omar, a Minnesota Democrat, could be heard shouting from the House chamber floor.

She called out: "You're killing Americans!" and added: "You have killed Americans!" She later shouted back: "You should be ashamed!"(Anadolu Agency, excluding headline)