After 12 protesters were killed and many of Basra's institutions torched last week, calm returned to the city late Saturday as Abadi's political rivals in Baghdad announced their intention to form Iraq's next government without him.

Protests first broke out in July in oil-rich Basra province before spreading to other parts of the country, as demonstrators demanded jobs and condemned corruption among Iraqi officials.

Anger in Basra flared on Tuesday over a growing health crisis, after more than 30,000 people were hospitalised by pollution in the city's water supply.

Since then, protesters have flooded the streets, clashing with security forces and torching the provincial headquarters, the Iranian consulate and the offices of armed groups.

Twelve protesters have been killed in the clashes, with rights groups accusing security forces of using excessive force.

Officials have blamed the deaths and violence on "vandals" who infiltrated the demonstrators.

Abadi has scrambled to defuse the anger.

In July, authorities had already pledged a multi-billion dollar emergency plan to revive infrastructure and services in southern Iraq following the first wave of protests.

On Saturday, his government announced it would allocate an unspecified amount of extra funds for Basra.

But demonstrators were unimpressed, saying the billions of dollars pledged in July have failed to materialise.