The mother to detained Tanzanian journalist Erick Kabendera died on Tuesday, two weeks after pleading with President John Magufuli to have her son released.
Verdiana Mjwahuzi died on Tuesday at Amana Hospital in the capital Dar es Salaam, where she has been receiving treatment.
Mjwahuzi, 80, went viral on social media a fortnight ago when she sent a direct message to Magufuli. She was living with her detained son before he was arrested.
Kabendera was arrested in July for allegedly writing explosive corruption stories about the Tanzanian government.
However, the authorities charged him with money laundering and tax evasion charges but the case has dragged in court.
His lawyer, Jebra Kambole, has been fighting for his release in bail but authorities are yet to conclude on the case.
"We are asking the court that the prosecution speed up the investigation as the case has been postponed many times," Jebra Kambole is quoted in local media as saying after the latest delay.
Shortly after Kabendera's arrest, the US and UK embassies in Tanzania said they were "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".