Haleema Cadre from Kalmunai, a mother with an 8-year old son, her husband who is an Indian national and K M S Bandranaike from Kurunegala, has been sentenced to death, Arabnews reported.
They were alleged to have been involved in an armed robbery and murder of an elderly Saudi woman.
Another five Sri Lankans have also been sentenced to five years in jail and 500 lashes related to the same offence.
They are: Singarayar Calithar Wimaladas from Trincomalee, Abdul Basheer Mohamed from Mathurankuli, Puttalam, Amir Jabbar from Sammanthurai, Rismiya Abdul Haq from Kanatalai and Manickam Kulanthaivel Rosa from Kalmunai.
Amnesty international said Haleema was the mother of a young child.
"They have had no legal assistance at any time, even during trial and are believed to have confessed under duress," Amnesty said in a statement.
"None have had any legal representation whilst in detention or at any stage of the legal proceedings."
A Sri Lankan teenager who has been accused of