Unrest over Iraq's dire public services, while US troops prepare to end combat operations seven years after the invasion, has sharpened frustration with political leaders who have yet to form a government more than five months after an election.

Riot police scattered around 250 demonstrators on Saturday evening after they ignored a curfew imposed by local authorities on residents to prevent protesters from taking to the streets without permission, police sources in Nassiriya said.

Similar demonstrations occurred in Nassiriya in June when 1,000 protesters tried to storm the provincial council building, scuffling with police, and also in the southern oil hub of Basra, where two people died in clashes with police.

"The protesters threw stones at police forces, then riot forces moved to disperse them. They didn't have permission to demonstrate," a Nassiriya police source said.

Hospital officials at the Al-Hussain Hospital in Nassiriya said they received up to nine wounded, including six policemen suffering minor injuries.

Police said 37 protesters were arrested.

Incumbent Prime Minister Nuri Al-Maliki replaced the electricity minister in June after protests first erupted.

As the sectarian war recedes, complaints have been growing about public power lasting just a few hours each day, especially as summer temperatures regularly reach 50 degrees Celsius.

The growing public frustration coincides with a dangerous political vacuum following the March 7 parliamentary election that insurgents have sought to exploit through persistent attacks before the end of US combat operations on Aug. 31.

The US military says an American solider has been killed in southern Iraq.

The military said in a statement the solider was killed Sunday while conducting operations in the southern Basra province.

It was not immediately clear whether the soldier died as a result of hostile fire. The statement provided no details about the incident, saying only that it is under investigation.

This is the first fatality among US troops in Iraq since the last American combat unit left the country earlier this week.

The name of the deceased soldier was being withheld pending notification of next of kin.

The death raises to at least 4,416 the number of US military personal killed in Iraq since the war began in March 2003.