The effective loss of the capital of Iraq's largest province was Baghdad's worst military setback since it started clawing back land from the jihadists late last year.
Days after a rare message from IS supremo Abu Bakr al-Baghdadi urging mass mobilisation, the group came close to also seizing the heritage site of Palmyra in Syria, but the army pinned the jihadists back.
Iraqi Prime Minister Haider al-Abadi, the United States and the leadership of the Sunni province of Anbar had been reluctant to deploy Iranian-backed groups in Ramadi.
Hadi al-Ameri, a key figure in Hashed al-Shaabi and the leader of the Badr paramilitary group, argued Anbar's leaders should have taken up his offer sooner.
Badr's TV channel Al Ghadeer said Ameri "holds the political representatives of Anbar responsible for the fall of Ramadi because they objected to the participation of Hashed al-Shaabi in the defence of their own people".
Various militias announced they had units already in Anbar -- including around the cities of Fallujah and in Habbaniyah -- ready to close in on Ramadi and engage the city's new masters.
"Tomorrow, God willing, these reinforcements will continue towards Anbar and Ramadi and the start of operations to cleanse the areas recently captured by Daesh will be announced," Jaafar al-Husseini told AFP, using an Arab acronym for IS.
