Trump, the 69-year-old real estate tycoon, won two key states of Mississippi and Michigan in the second Super Tuesday showdown.
Celebrating his two victories, Trump criticised the establishment Republicans who have led recent attacks on him, including heavy negative advertising.
In Mississippi, he received the support of nearly 50 per cent of the Republican voters. He was followed a distant second by Senator Ted Cruz with 35.2 per cent of the votes counted.
Cruz won a Republican-only race in Idaho and Hawaii results are expected later in the day.
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Clinton had an impressive win in the US State of Mississippi, as a result of which she was able to have more delegates in her kitty as against Sanders.
She won Mississippi by 88 per cent to 10 per cent, bolstered by her overwhelming support among African American voters.
Clinton was expected to have an easy win in Michigan, where according to some polls she was leading by more than 20 points.
But when results came in, Sanders won the support of 50 per cent of the Democratic voters, while 48 per cent supported Clinton. The victory in Michigan has given Sander's campaign a bounce ahead of the vital March 15 primaries in Florida, Ohio and three other big states.
Despite the upset in Michigan, Clinton still has a lead in the number of delegates, which is crucial for winning the party's presidential nomination.
Some 21 states have so far had their say in the Democrat primaries and caucuses, with Clinton winning 12 and Sanders claiming nine.