The United States and Britain voiced concern Friday at the "steady erosion of due process" in Tanzania, raising particular issue with the arrest of a respected journalist and government critic.
Erick Kabendera, known for his unflinching coverage of President John Magufuli, was charged this week with organised crime and financial offences after being arrested by plainclothes police at his home on July 29.
His detention provoked outrage, with rights groups demanding Mr Kabendera be released and warning that the case reflected worsening press freedoms under President Magufuli, who came to power in 2015.
Mr Kabendera, a reporter for local and international press outlets, was initially detained for questioning over his citizenship before the charges were upgraded to sedition.
But both lines of inquiry were dropped, and Mr Kabendera was charged Monday in a Dar es Salaam court with tax evasion, money laundering and organised crime.
"The US Embassy and the British High Commission are deeply concerned about the steady erosion of due process in Tanzania, as evidenced by the ever more frequent resort to lengthy pre-trial detentions and shifting charges by its justice system," the two countries said in a joint statement.
"We are particularly concerned about a recent case -- the irregular handling of the arrest, detention, and indictment of investigative journalist Erick Kabendera, including the fact that he was denied access to a lawyer in the early stages of his detention, contrary to the Criminal Procedures Act."
Reporters Without Borders (RSF) has labelled Mr Magufuli a "press freedom predator" and dropped Tanzania 25 places on its annual press freedom index this year.
Mr Kabendera had written about being stalked and harassed in the years since President Magufuli's election, and he is not the only journalist to be targeted.
Mr Magufuli has shut down newspapers, banned opposition rallies, switched off live broadcasts of parliamentary sessions and used the cybercrimes law to jail critics.
Azory Gwanda, a Tanzanian journalist and government critic who disappeared in 2017, has never been found.
Mr Magufuli came to power as a corruption-fighting "man of the people" but has since been criticised for his authoritarian leadership style.