The rights group said on Wednesday that Rajab should be released immediately since he is jailed solely for exercising his right to freedom of expression.
"Like many others in Bahrain, Rajab is a prisoner of conscience, jailed solely for peacefully exercising his right to freedom of expression," said Ann Harrison of Amnesty’s Middle East and North Africa program on Wednesday adding that "he should be released immediately and all other charges or convictions against him dropped or overturned."
A Bahraini court on Monday sentenced Rajab to three months in prison over his online comments.
Although prosecutors say he is jailed because his comments insulted Sunni population of the province of Muharaq, it is widely believed that he was put behind bars because his tweet was against the ruling Al Khalifa family, especially Bahraini Prime Minister Sheikh Khalifa bin Salman.
Rajab’s tweet suggested that residents of the Muharraq district had made a show of support for PM Sheikh Salman only because he had offered them subsidies. A group of retired army and security officers, who are seen as pro-government, filed a complaint against Rajab shortly after his tweet.
According to Rajab’s lawyer, the activist’s time behind bars will likely be shortened because he already served three weeks in detention.
Rajab, the president of the Bahrain Centre for Human Rights, also faces charges related to anti-government protests in the Persian Gulf state. He is accused of organizing and taking part in protest demonstrations.