Dozens of protesters have been killed and hundreds more injured in clashes with police since popular unrest swept across parts of Iraq's south beginning on October 1, when thousands took to the streets demanding jobs, an end to corruption and what they said was Iran's meddling in Iraq's internal affairs.
Late last month, Abdul-Mahdi first agreed to step down, pending an agreement on a replacement by the various factions in government.
In a pre-recorded speech, Abdul-Mahdi referred to the rising death toll by security forces.
The turmoil in Iraq, along with sustained rallies that removed the prime minister of Lebanon, pose a particular challenge to Iran, which wants to protect the significant sway it holds over politics in both countries.
But parliament is set to convene an emergency session on Sunday (December 1) to discuss the crisis.
Weeks of political wrangling are expected before a successor to Abdul Mahdi is picked and a new government formed.
The move by Adel Abdul-Mahdi 13 months after he took over as prime minister triggered celebrations by anti-government protesters who have been camped out in Baghdad's Tahrir Square for almost two months.
The statement did not specify when he would tender his resignation.
Iraqi protesters have welcomed the resignation but say it is not enough.
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Iraq's constitution, drafted in 2005, does not include a provision for the resignation of the premier, so his intention to submit a letter to parliament would trigger a no-confidence vote.
"My understanding is this will be taken care of per Article 61", he said.
Earlier on Friday, Sistani had urged parliament to drop its support for the current cabinet following the unrest. The official spoke on condition of anonymity in line with regulations.
Officials traded theories as to why Abdul-Mahdi chose to tender his resignation through parliament, with some speculating it was to buy more time or avoid the risk of a vacuum should the post remain empty.
Abdul-Mahdi, a former finance minister, was picked by rival Shiite Muslim groups as a consensus candidate following parliamentary elections in 2018, but has struggled to form a strong government and start the nation's recovery from a devastating war with Islamic State jihadists.
In his speech, addressing these speculations, Abdul-Mahdi said he was acting on the advice of Iraq's chief Supreme Court judge.
"This is a positive thing.it show's were no longer a dictatorship - governments do resign, and this is how authority is in democratic countries", he said.
Iraq has sent military and police forces to the oil-rich areas in the south to secure the re-opening of roads that had been closed by protesters. "We need to be fair to our people and listen to them, where we made mistakes, where we did not make up for the mistakes of previous governments".