The month-long trial, which ended Wednesday, was held behind closed doors in western Kazakhstan, and few details have been made public.
One group of 42 defendants was jailed on charges including forming a terror group, financing extremist activity and organizing a series of attacks. The remaining five defendants, who were tried in a parallel case at a separate location, were linked to specific attacks in the western oil city of Atyrau in October.
The defendants ranged in age from 22 to 32 years old. Local newspaper Ak Zhaiyk reported that they included two citizens of neighboring Uzbekistan.
The lack of transparency in the case has raised concerns over the fairness of the trial.
Western Kazakhstan-based rights activist Togzhan Kizatova told Radio Free Europe/Radio Liberty that the relatives of the accused had been pressured not to seek assistance from advocacy groups.
"They told me they were afraid, that they were being threatened," Kizatova said. "It is natural that the parents are afraid, they say they want their relatives to get out alive."
Officials say several other individuals also wanted on terrorism charges have fled the country.
The killing of two police officers in western Kazakhstan last June was linked to indigenous terrorist groups and prompted security operations in which two more police officers and nine suspected terrorists were killed.
The Jund al-Khilafah militant group claimed responsibility for two blasts in late October in Atyrau. Only one person—the man engaged in setting the bombs—was killed. The group of five defendants convicted Wednesday were jailed in connection with these attacks.