Polling day unfolds smoothly across US after massive turnout by early voters

People queuing up to vote in a shopping centre in Reno, Nevada (AP Photo/Godofredo A. Vasquez)

Polling day has unfolded relatively smoothly across the United States with only scattered disruptions and delays.

Leading into Tuesday, more than 82 million Americans had already cast their ballots in a largely successful early voting period with high turnout despite some hiccups and frustrations in the presidential battleground of Pennsylvania.