The Navy said the six Indians had in their possession 13.5 kg of drugs.
The suspects were disguised as fishermen, navy spokesman Chaminda Walakuluge said.
“Drug smugglers operate disguised as fishermen,” Walakuluge told AFP. “We are on alert for drugs coming in.”
He said the navy has seized a total of 130 kilos (286 pounds) of heroin and cocaine and 2,140 kilos (4,708 pounds) of cannabis in the past year and arrested a total of 19 Indians during the same period.