A second day of sometimes dueling demonstrations over the integrity of the U.S. presidential election started early on Thursday in Philadelphia and other cities as ballot counting dragged on in a handful of states that will decide the outcome.

Iran PressAmerica: Supporters of Joe Biden have rallied around the slogan to "count every vote," believing a complete tally would show the Democratic former vice president had beaten Republican candidate and current US President Donald Trump.

Ardent Trump supporters have countered with cries to "protect the vote" in support of his campaign's efforts to have some categories of ballots, including some votes submitted by mail, discarded.

Both factions appeared outside a vote-counting center in Philadelphia on Thursday morning, where election staff steadily worked through a mountain of still-uncounted mail-in ballots that will determine whether Biden or Trump will take Pennsylvania's crucial 20 Electoral College votes.

Read More:

Joe Biden launches transition website

Nancy Pelosi Says Joe Biden will win electoral college in 'historic' election