Iraq's parliament speaker threatened the electricity minister Tuesday with a vote of no confidence if he does not appear within four days to be quizzed over a persistent power crisis.

For weeks, demonstrators have protested against corruption and poor services, especially abysmal power provision, making minister Qassem al-Fahdawi a prime target for popular anger.

Parliament speaker Salim al-Juburi "warns the electricity minister that he will be held accountable in absentia and that confidence will be withdrawn from him if he does not attend by Saturday at the latest," a statement from his office said.

Juburi also said he rejected a request from Fahdawi that he not have to appear.

Amid a major heatwave that has seen temperatures top 50 degrees Celsius (120 degrees Fahrenheit), thousands of people have protested in Baghdad and cities in the Shiite south to vent their anger and pressure the authorities to make changes.

They have railed against the poor quality of services, as power cuts leave just a few hours of government-supplied electricity a day during the scorching summer heat.

Their demands were given a boost when top Shiite cleric Grand Ayatollah Ali al-Sistani called on August 7 for Prime Minister Haider al-Abadi to take "drastic measures" against corruption.

Sistani, who is revered by millions, said that "minor steps" announced by Abadi were not enough.

Abadi rolled out a reform programme two days later.

Parliament signed off on Abadi's proposals as well as additional reforms, and the prime minister has begun issuing orders for changes, including cutting 11 cabinet posts and slashing the number of guards for officials.

But even with popular support and backing from Sistani, the fact that parties across Iraq's political spectrum benefit from graft is a major obstacle to the nascent reform effort.