Police Spokesman ASP Ruwan Gunasekara said the arrested suspects include two American nationals, one Afghan national and two Sri Lankan residents of Hikkaduwa.
The arrests were made following a joint operation carried out by the Police Special task Force and the Police Narcotics Bureau.
The suspects were arrested along with the drugs inside an apartment in the first floor of the building while the heroin was found packed into 92 parcels, weighing one kilogram each.
The seized heroin haul is estimated to be worth around 1,141 million rupees,
The arrested American nationals are aged 29 and 45 while the Afghan national is 41 years of age.