A Swedish court said on Thursday it had found a former security services and armed forces employee and his brother guilty of spying for Russia.
The men, aged 42 and 35, were detained last year and have denied all allegations. Their lawyers were not immediately available for comment on Thursday.
"The district court convicts two brothers of aggravated espionage and the older brother of unauthorized handling of classified information," the Stockholm district court said in a statement.
It said it had sentenced the older brother to life imprisonment and the younger brother to a term of nine years and 10 months.
The brothers stood trial on suspicion of providing the Russian intelligence agency GRU with classified information for a decade.