Several people — including a number of children — also drowned over the weekend as they attempted to flee the besieged city by crossing the Euphrates River.
Abadi's decision to halt, two days after elite Iraqi troops poured into the city's rural southern outskirts, postpones what was expected to be one of the biggest battles ever fought against Islamic State.
The Iraqi army is advancing slowly against Islamic State militants barricaded in the city. Caught in the middle, more than 50,000 civilians are trapped, and at grave risk.
The battle for Fallujah is shaping up to be one of the biggest ever fought against Islamic State, in the city where US forces waged the heaviest battles against the Sunni Muslim militant group's precursors.
The sighting comes days after US special operations troops were photographed and videotaped in Syria on the front lines of a major Kurdish-led offensive against the Islamic State.
Iraqi government security forces and allied militias continued their assault on the Islamic State-held town of Fallujah on Wednesday, killing more civilians than militants in the process, according to sources inside the city.
Iranian Revolutionary Guard Commander Qassem Suleimani made an appearance with Iraqi Shiite militias outside Fallujah as the UN warned that as many as 10,000 civilians remain trapped inside the Islamic State-held town.
The protesters included supporters of powerful Shia Muslim cleric Moqtada al-Sadr, who expressed support for what he called a "peaceful spontaneous revolt."
Islamic State, which controls swathes of the Iraq's north and west, has carried out a string of bombings this week that killed around 100 people.
The first attack in the Iraqi capital during Wednesday rush hour saw an SUV packed with explosives detonate outside a beauty salon near a bustling market in the Sadr City district.