Istanbul - A prominent Bahraini human rights activist, Nabeel Rajab, was arrested because of critical messages he posted on Twitter about the Interior Ministry, campaigners say.
Rajab, the head of the Bahrain Centre for Human Rights, will have to appear on Thursday before the public prosecution for further investigation.
During the 2011 uprisings against King Hamad al-Khalifa, a Sunni, Rajab was a leader of the protest movement. The demonstrations were subsequently crushed. The country is majority Shiite but ruled by the Sunni monarchy.
After returning to his country from Europe on Wednesday, Rajab was arrested for tweets that were alleged to have "denigrated government institutions."
The government has not confirmed which tweets it deemed offensive, but Rajab had posted about Bahrainis from the security forces allegedly fighting along with the Islamic State group in Iraq and Syria.
The Gulf Centre for Human Rights (GCHR), which confirmed his arrest, said the alleged crime is punishable by up to three years in jail and noted that Rajab had only been released from prison in May after a two-year sentence.
Maryam Al-Khawaja, another activist, was arrested in August.
Leading human rights groups are calling for the release of human rights activists in Bahrain.
"His arbitrary detention and judicial harassment merely aim at hindering his human rights activities," said the Observatory for the Protection of Human Rights Defenders.