"They were an unruly mob which attacked the police in a breach of peace," police spokesman Ruwan Gunasekera said after the arrests.
Hundreds of rioters who gathered near the court premises were demanding stern action against five suspects arrested for the murder of an 18-year-old school girl from Jaffna's Punguduthivu town, angered by the police's delay in producing them in court.
The girl's body was found on May 14 in an abandoned house.
Gunasekera said the five policemen who were injured when rioters attacked police with stones were under treatment at Jaffna hospital.