Abadi flew straight into the city from Brussels where he attended a NATO summit to discuss the Islamic State group, and immediately held talks with officials, a statement said.

As Abadi met the governor of the oil-rich province and the head of the power company, Iraq's top Shiite authority voiced support for the protesters, calling Basra one of Iraq's "most miserable areas".

"It is not fair and it is never acceptable that this generous province is one of the most miserable areas in Iraq," Abdel Mehdi al-Karbalai, the representative of Grand Ayatollah Ali al-Sistani, said at Friday prayers in Karbala.

Giving the weekly sermon, Karbalai said many residents of Basra "are suffering from a lack of public services" and urged the "federal and local government to deal seriously with the demands of citizens and work urgently to do what can be done."

The protests erupted on Sunday and security forces opened fire killing a protester, sparking further anger.

Demonstrators set tyres ablaze to block roads and tried to storm government installations.

As well as unemployment, those involved are frustrated by rising living costs and a lack of basic services in the city, the capital of Basra province.

Hundreds of demonstrators waving Iraqi flags gathered Friday in front of the provincial headquarters in Basra city centre, with security forces including riot police deployed heavily.

"People are hungry, there is no water, no electricity," protester Abdullah Khaled, 29, told AFP.

"Our simplest demands are job opportunities, water desalination projects, and the construction of power plants."

Cleric Karbalai urged the demonstrators to refrain from violence, warning them against being influenced by "unruly individuals or those acting in self-interest".

- Oil wealth but jobless -

In an apparent first step to calm frayed nerves, Abadi ordered local officials to sort out "the legal status" of security guards employed by the interior ministry at oil installations, his office said.

These guards receive no benefits and work without contracts unlike their peers at the interior ministry.

At a later meeting with local tribal leaders Abadi pledged to "spend the necessary funds for Basra, including on services and reconstruction", a source close to the PM told AFP.

On Thursday Oil Minister Jabbar al-Luaibi said protesters tried to break into an oil installation in the West Qurna 2 oil field of Basra province.

In a statement released by his office, Luaibi said the demonstrators failed to enter the area but had set fire to a gate and a security post.

Officially, 10.8 percent of Iraqis are jobless, while youth unemployment is twice as high in a country where 60 percent of the population are aged under 24.

Abadi has vowed to rebuild the economy, ravaged by years of conflict, but frustrations have been growing especially in the oil-rich south.

Iraq is the second biggest producer of crude in the OPEC oil cartel, with 153 billion barrels of proven reserves.

The oil sector accounts for 89 percent of the state budget and 99 percent of Iraq's export revenues, but only one percent of jobs as the majority of posts are filled by foreigners.