An aide says a nephew of Iranian opposition leader Mir Hossein Mousavi was killed in fighting between protesters and security forces.

The close aide to Mousavi says the nephew, Ali Mousavi, died of wounds in a hospital on Sunday.

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The aide spoke on condition of anonymity because of fears of reprisals from the government.

A reformist Web site, Parlemannews.ir, also says Mousavi's nephew was killed.

Opposition Web sites and witnesses say security forces fired on anti-government protesters in the capital Sunday, killing at least four people in the fiercest clashes in months.