Washington DC and cities across the US ramped up security ahead of US President-Elect Joe Biden's inauguration, amid warnings of possible political violence even after the January 20 swearing-in.

Delta, Alaska, American, and United Airlines also announced on Thursday they will not allow travelers flying to Washington area airports to check firearms on its flights before the inauguration.

The actions follow the storming of the US Capitol last week by supporters of President Donald Trump and disturbances on flights and at airports. Officials have warned of plans for armed protests in Washington and all 50 states.