Philadelphia - Police officers were posted at street corners in down town Philadelphia as the first protesters hit the city's sweltering streets on Sunday ahead of the Democratic National Convention.Several demonstrations were planned, including an anti-fracking march from City Hall to Independence Mall, near the Liberty Bell. Bernie Sanders supporters expect about 3 000 protesters will join them in a march from City Hall to a park near the convention site in the afternoon.The heat wave that descended on the city was showing no mercy, with temperatures expected to reach the upper 30°C and the city under an "excessive heat" warning. It's expected to peak on Monday, the convention's first day. Crowds braving the weather could take advantage of "misting tents" and free water, compliments of the city.Parking The first march on Sunday had the perennial problem in Philadelphia: parking. DC to DNC organiser Ed Higgins said finding parking spots and organising the crowd delayed his group's march, which got going about an hour late.The group of about a dozen marchers walked on side walks from near the convention site up toward the Liberty Bell. One played "This Land is Your Land" on bagpipes as the group weaved around people eating brunch at side walk cafés and others walking dogs.Higgins is part of a pro-Sanders group that walked 220km over nine days from Washington, arriving on Saturday evening. He closed his marketing company in Tempe, Arizona, last month and is a full-time activist pushing for fair elections, racial justice and living wages.He said he intends to be arrested "a couple of times" during the convention."We're protesting a false democracy," Higgins said.He said Sanders supporters and others had votes suppressed in presidential primaries.Earlier on Sunday morning, a stage was being readied for rallies in FDR Park - the designated protest zone across the heavily barricaded street from the convention site - and people who camped out against a city edict readied for their actions around the city.Among them was protester Dan Martin, who travelled 12 hours from Augusta, Georgia. He had an anti-Hillary Clinton sign portraying her as beholden to Wall Street. "This is all you need to know about her," he said.The protests come as Sanders called for the head of the DNC to step down after leaked emails suggested the party played favourites during the presidential primary.Emails posted to the website WikiLeaks show that at least some DNC officials were looking at ways to undercut Sanders' campaign, including questioning his religious beliefs.Sanders told ABC's This Week on Sunday morning that the party chair, Debbie Wasserman Schultz, should resign immediately.More than 5 000 delegates are among the 50 000 people set to attend the gathering at the Wells Fargo Centre in South Philadelphia, which is expected to culminate with Clinton being named the party's official nominee for president.The former secretary of state and first lady has named Senator Tim Kaine of Virginia as her running mate.