NEW DELHI — At least 30 people were killed Friday when violent clashes spread across northern India after a popular spiritual guru was convicted of rape and his followers flooded the streets, smashing cars, torching buses and attacking police officers.

More than 200 people were also injured in the clashes, which began in the city of Panchkula and quickly spread, according to local authorities.

The spiritual leader, Gurmeet Ram Rahim Singh — known as “the guru of bling” — has millions of followers. The Indian authorities had anticipated trouble ahead of a verdict.

A judge found Mr. Singh guilty of two counts of rape in a 15-year-old case in which two women said they were attacked at the headquarters of his sect. Mr. Singh, dressed in long white shirt and dhoti — a garment worn by Hindu men that wraps around both legs — was taken into custody after the verdict. His sentence will be announced next week.