The latest protests were held in Abadan, 12 kilometres from Khorramshahr, where 11 people were hurt Saturday when an unidentified gunman opened fire during a demonstration, according to officials.
State-run IRNA news agency did not specify how many people were involved in the Abadan demonstration, but said security forces had broken up a crowd that was "disrupting public order".
It said people protesting over poor water quality in a western district of the city had thrown projectiles and set fire to rubbish bins and a vehicle.
Several injured during Iran water protests
The agency did not report any further injuries, but added that water pollution in the two cities of Khuzestan province had sparked several demonstrations over the past four days.
Iran's leaders seek ways to defend economy from US sanctions
The province was devastated by the eight-year war between Iran and Iraq in the 1980s and suffers from chronic pollution and drought.
It has a largely Arab population that has long complained of official discrimination.
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