Philadelphia police have briefly detained more than 50 people after they tried to storm the barricades outside the Democratic convention in a show of anger over Bernie Sanders' treatment by party leaders, even as he urged his supporters to fall in line behind Hillary Clinton.
Several hundred Sanders supporters and other demonstrators converged in the sweltering heat on Monday evening at the convention site as the gathering was being called to order, chanting "Nominate Sanders or lose in November!" and "Hey, hey, ho, ho, the DNC has got to go!"
They carried signs reading, "Never Hillary," "Just Go to Jail Hillary" and "You Lost Me at Hillary".
As tensions mounted outside the Wells Fargo Center, police moved metal fences into place and closed the nearest subway station to arriving trains.
Fifty-five people were issued citations for disorderly conduct when protesters tried to climb over police barricades at the edge of the security zone surrounding the convention, police said.
The anger reflected the widening rift inside the Democratic Party and the convention hall itself between Sanders' supporters and Clinton's.
Debbie Wasserman Schultz resigned as Democratic Party chairwoman on Sunday over leaked emails suggesting the supposedly neutral Democratic National Committee played favourites during the primaries by siding with Clinton and bad-mouthing Sanders.
Speaking to delegates Monday morning, Sanders implored them to vote for Clinton, generating a chorus of boos.
"Brothers and sisters, this is the real world that we live in," Sanders said. Donald Trump "is a bully and a demagogue".
The protests took shape amid a punishing heat wave, with oppressive humidity and temperatures in the mid-90s, along with the possibility of severe thunderstorms in the evening. The Fire Department handed out bottled water, and a few protesters were treated for heat-related problems.
The citations capped a day of demonstrations around the city on the opening day of the convention.
Tensions rose when about 50 marchers sat down on Broad Street and refused to move unless the Mississippi state flag with the Confederate emblem was taken down from a lamppost. The flags of all 50 states fly from light poles on the street.
Two officers stood in front of the lamppost, not allowing anyone to climb it, as hecklers jeered: "Think for yourself. Be a real man."
City officials later removed the flag.
