A gunman shot two Democratic state lawmakers in Minnesota early Saturday, killing one and her husband and wounding the other, in what the northern US state's governor said were "politically motivated" attacks.

The shootings came at a moment of deep political divisions in the United States, as thousands prepared to take to the streets in protest at the policies of Republican President Donald Trump.

The suspected assailant was still at large, officials said, with a massive manhunt underway.

US President Donald Trump and Attorney General Pam Bondi decried what they called "horrific violence" and said the perpetrators would be prosecuted to "the fullest extent of the law." State representative Melissa Hortman -- the former speaker -- and her husband Mark were killed at their home near Minneapolis, Governor Tim Walz told a press conference.