The city police estimate between 35,000 and 50,000 protestors on the streets of Philadelphia on an average of each of the four-day convention, while anti-Clinton activists claim the number to be 100,000.
The group of protestors range from supporters of Senator Bernie Sanders who lost to Clinton during primaries, to labour unions and anti-war groups.
Yesterday, thousands of Sanders' supporters marched through the streets of Philadelphia sweltering heat in the first major protests ahead of the convention from today.
Another group describing itself as "Occupy DNC Convention July 2016" held a peaceful rally with the objective of swinging super delegates to Sanders.
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Protests in Philadelphia come soon after similar protests were held by thousands from anti-Trump group in Cleveland last week that hosted the Republican National Convention, which overall was peaceful, even though the city was on its edge.
In a statement, the Philadelphia police extended its full cooperation to the protestors as long as it was peaceful.
Cheri Honkala, the organiser for the Philadelphia-based PPEHRC, said her group's demonstration is meant to put a spotlight on the plague of homelessness and poverty in the city.
PPEHRC stands for People People's Economic Human Rights Campaign.
Some of the labour unions also plan to hold protests in the city, demanding a USD 15 billion per hour as minimum wage.
Code Blue, which is known for its campaign against wars in Afghanistan and Iraq and use of drones, have also announced to hold protests in Philadelphia.
The Philadelphia chapter of the National Organisation for the Reform of Marijuana Laws has announced its plans to march a 51-foot "joint" from City Hall to the Wells Fargo Center, the venue of the Democratic National Convention.
An anti-fracking group has also announced to hold a protest rally.
The police said it has taken appropriate security measures.