He won Florida, Ohio, Iowa and North Carolina, while Democrat Clinton took Virginia and Nevada. Pennsylvania is too close to call.
New Hampshire, Michigan and Wisconsin – which were meant to be part of the Clinton firewall – are deadlocked, too.
Markets lurched as Mrs Clinton’s path to victory began to narrow.
The US dollar and Mexican peso plummeted while the Dow futures dropped 800 points.
Mr Trump is closing in on the 270 out of 538 electoral college votes needed to declare victory.
His Ohio win was a big boost, as no Republican has ever taken the White House without winning the Midwestern bellwether.
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