Bahraini authorities arrested prominent rights activist, Nabeel Rajab, in a raid on his home early Monday, family members and a rights group said.
The reason for the arrest was not immediately clear.
Sayed Ahmed Alwadaei, director of advocacy at the London-based Bahrain Institute for Rights and Democracy (BIRD), condemned the move as "abhorrent and reflective of the government's repressive nature."
Rajab's latest arrest comes two weeks after prominent opposition activist Zainab al-Khawaja was freed from jail on what prosecutors said were humanitarian grounds.
In July last year, Rajab was freed after Bahrain's King Hamad bin Isa Al Khalifa pardoned him on medical grounds.
He had been serving a six-month sentence over comments on Twitter criticizing the defence and interior ministries, prison conditions in Bahrain and the Saudi-led war against Yemen's Houthi rebels.
Rajab had previously completed a two year sentence for his part in pro-democracy protests in the Sunni-ruled, Shiite-majority Gulf state.
Bahrain saw a wide protest movement in February 2011 in the wake of popular uprisings that unseated long-standing dictators in Tunisia and Egypt.
But security forces, backed by troops from neighbouring Saudi Arabia, cracked down on the demonstrations, leaving more than 100 civilians dead, according to opposition figures.
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