The arrests were made on a tip-off early on Sunday from the port city's Patenga area, RAB-7 Assistant Director Mimtanur Rahman told bdnews24.com
He said 600,000 yaba tablets were found in possession of the Myanmarese.
Details of the haul will be provided later at a media briefing, said senior officer Rahman.
Yaba tablets are a combination of methamphetamine and caffeine, and a popular substitute for the party drug Ecstasy.
It made its way into Bangladesh's party scene in early 2000.
A series of sensational raids in 2007 and media coverage on the issue brought the drugs into limelight that year, leading to calls for stopping their use.
Methamphetamine, the key component of Yaba, is highly addictive and causes withdrawal symptoms such as irritability, insomnia, confusion, tremors, convulsions, anxiety, paranoia, and aggressiveness.
Yaba is usually smuggled into Bangladesh through 45 routes of Cox’s Bazar district, bordering Myanmar's Rakhine State, according to intelligence agencies.
Myanmar is infamous for producing yaba, opium and cannabis in vast quantities.
Drug trafficking has emerged as a problem in Rakhine State and illicit drug trade has flourished because of its mountainous land and porous borders.