Australia has imposed financial sanctions and travel bans on seven Russian prison officials after the nation’s opposition leader, Alexei Navalny, died in custody, Report informs via The Northern Daily Leader.

Until his death on February 16, Mr. Navalny had been held at the “Polar Wolf” Arctic penal colony, which the government says was known for its systematic abuse of prisoners.

These latest sanctions are part of the federal government’s attempts to hold to account those responsible for the death of Russian President Vladimir Putin’s most formidable domestic opponent.

“He was regularly mistreated, denied healthcare, and placed in prolonged periods of solitary confinement,” a government statement said.