US election results LIVE: Harris or Trump? Who's winning presidential race as vote-counting begins?

The votes are all in. Millions of Americans formed long lines to cast their ballots while thousands of US expats from around the world, made their voices heard through mailed and online votes.

Now the wait begins. Kamala Harris and Donald Trump notched up early wins on Election Night, November 5, as the first key polls closed in one of the tightest and most volatile elections in US history.

The outcome — which could be known overnight — will have momentous consequences, either making Harris the first woman in the world's most powerful job or handing a historic comeback to Trump and his right-wing "America First" agenda.

Here's what we know so far:

Results are tumbling in, with US media projecting wins for Trump so far in Alabama, Arkansas, Florida, Indiana, Kentucky, Louisiana, Mississippi, Missouri, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, West Virginia and Wyoming.

Harris has so far captured Delaware, Illinois, Maryland, Massachusetts, New York, Rhode Island, Vermont and the US capital Washington, DC.

So far, that gives Harris 81 electoral votes and Trump 168.

The magic number to win the presidency is 270. Observers expect the hotly contested race for the White House to come down to a handful of key battleground states.

Expected challenges emerged as polls drew to a close.

In a stark reminder of the tension — and fears of outright violence — around the election, officials said 32 bomb threats were called into polling locations around Georgia.

In five stations, the threat required temporarily suspending voting while police checked for explosives, Fulton County police chief said.

The FBI and local authorities said the threats appeared to originate in Russia, which is accused by Washington of trying to meddle in the election.

There were no surprises in the initial results. Republican former president Trump won strongholds Indiana, Kentucky and West Virginia, and Democratic vice-president Harris took more liberal Vermont.

As the first results came in, Trump said "we're going to have a big victory tonight."

The Harris campaign reported strong turnout in the Democratic stronghold of Philadelphia.

Harris, 60, would also be only the second Black and first person of South Asian descent to be president.

She made a late, dramatic entrance into the race when Biden dropped out in July, while Trump — twice impeached while president — has since ridden out two assassination attempts and a criminal conviction.