Washington DC - Former President Barack Obama has hailed Democrats' decisive victory in the midterm elections as a "clear message" from voters.

The Democrats wrested control of both the House of Representatives and the Senate from President Donald Trump's Republicans in Tuesday's elections.

The results marked a decisive rebuke of the Trump administration with two years left in his term.

"They want a politics that brings people together rather than divides them, and leaders who offer concrete solutions to the challenges they face," Obama wrote of American voters on social media.

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"These results were only possible because outstanding candidates stepped forward in every region of the country – including in areas once considered long shots," the Democrat continued.

"While this administration has another two years in office, our job now is to roll up our sleeves, make changes wherever we have the power to do so, prevent further damage, and lay the groundwork for the future."

Obama's most prominent campaign appearance was alongside Dr. Abdul El-Sayed, who won the US Senate race in Michigan to become the first Muslim elected to the chamber.