The Palestinian Youth Movement (PYM) and its coalition organized the event to commemorate what they're calling a year of genocide carried out by Israel in Gaza.
Huge rallies were also held across the world, with gatherings expected to continue over the weekend and peak on Monday, the date of the anniversary.
Pro-Palestinian demonstrators also gathered at New York's Times Square to call for a cease-fire, chanting "Gaza!" to a drumbeat. Some wore keffiyeh scarfs, waved Palestinian and Lebanese flags and held a large cardboard image of Israeli Prime Minister Benjamin Netanyahu with red paint symbolizing blood across his face.
Rallies were also planned in several other cities in the United States as well as in other parts of the world, including Denmark, Switzerland, South Africa and India. In the Philippines, dozens of left-wing activists protested near the U.S. Embassy in Manila, where police prevented them from getting closer to the seaside compound.
Pro-Israeli demonstrations are expected to be held Sunday because Jews across the world are still observing Rosh Hashana, or the Jewish new year.
This year, emotions will be high for many given that the midpoint of the 10 days spanning Rosh Hashana and Yom Kippur is Oct. 7 - the one-year anniversary of the Hamas attack that killed 1,200 Israelis and triggered the ongoing war in Gaza.
The Associated Press contributed to this report.