A charismatic former actress who later joined politics and became the top elected official in the southern Indian state of Tamil Nadu was found guilty Saturday of corruption in a landmark case filed 18 years ago.

Jayaram Jayalalitha will have to step down as chief minister of Tamil Nadu after a court in Bangalore found her guilty of possessing wealth disproportionate to her known sources of income.

The court was to hand down its sentence later Saturday.

Security was tight outside the court, with more than 5,000 police officers and paramilitary troops throwing a security cordon around the building. Roads were blocked 2 kilometers (about a mile) from the court to keep away Jayalalitha's supporters, who threatened to hold protests against the verdict.

Across Tamil Nadu, shopkeepers closed their stores and police were on alert.

Jayalalitha, 66, was accused in 1996 of amassing a fortune of 660 million rupees ($11 million) at a time when she was taking a token 1 rupee as her monthly salary.

Her supporters say the case is a political conspiracy to discredit her.

Indian politicians are rarely convicted for corruption, and even more rarely end up spending time in jail. Court cases move so slowly through India's judicial system that decades can go by without a verdict.

Jayalalitha joined politics in the early 1980s after a successful film career in southern India that included appearances in nearly 150 films. She has had three stints as chief minister of Tamil Nadu, including her latest one, which began in May 2011.