Civil rights groups and academics in India and the US have called on India's government to free a leading public health specialist and human rights activist, Dr Binayak Sen.
He was sentenced to life in prison last Friday for helping Maoist rebels.
Dr Sen was found guilty of carrying messages and setting up bank accounts for the rebels, who are active in large areas of central and eastern India.
Activists say the evidence against Dr Sen was "manufactured".
The human rights group Amnesty International has said his trial violated international standards.
"We are deeply shocked by the judgment of a Chhattisgarh [central Indian state] court holding Dr Sen to be guilty of sedition, and sentencing him to life imprisonment," said a statement signed by US author Professor Noam Chomsky, Indian historian Prof Romila Thapar and dozens of well-known Indian academics.
"As a doctor he served the people with devotion and helped to save many lives; as a human rights activist he stood up in defence of the rights of the downtrodden."
"And yet he has been handed down this sentence whose savagery is unbelievable."
The statement calls on the higher judiciary to "hear his appeal expeditiously, must grant him immediate bail till the end of the appeal process, and must judge his case with enlightened reason".
The court in Chhattisgarh found Dr Sen and three others guilty of treason and sedition and Dr Sen, who was out on bail since May 2009, was arrested.
He was first arrested from Bilaspur town in May 2007 for alleged links with Maoist leader Narayan Sanyal, whom he used to visit in jail.
India's Supreme Court ordered his release on bail two years later.
Dr Sen, a trained paediatrician, says he does not support the Maoists.
A senior member of the local unit of a leading Indian human rights group, the People's Union for Civil Liberties, he worked with poor tribal people in Chhattisgarh.
He ran a weekly clinic for the tribals and was piloting a community-based health programme.
Dr Sen was also awarded the prestigious Jonathan Mann Award for Global Health and Human Rights for his services to poor and tribal communities and his unwavering commitment to civil liberties and human rights.
His efforts in public health programmes helped to bring down the infant mortality rate in the state and deaths caused by diarrhoea and dehydration, say local doctors.
Dr Sen has been outspoken about the ways in which the government is trying to tackle the Maoists in Chhattisgarh by backing a controversial civil militia of local tribals called Salwa Judum.
He has also expressed his deep concern over rising inequality in India despite the economic boom.