Bahraini security forces detained family members of three U.K.-based activists over their protests against the gulf king's attendance at a royal horse show in Britain, one of the activists said.
The activists have been protesting against King Hamad's attendance at the Royal Windsor Horse Show. State-run Bahrain News Agency photographs have shown King Hamad with Britain's Queen Elizabeth II.
Sayed Ahmed Alwadaei, the director of advocacy at the London-based Bahrain Institute for Rights and Democracy, said his sister had received a call summoning her to Muharraq police station for interrogation on Saturday morning.
"This is a new law by the Bahraini authorities: blackmailing activists by detaining their family members in Bahrain," said Alwadaei.
The father and sister of two other activists also informed their family members that they were being held.
Alwadaei's family members were previously detained in October, after he shouted at a car carrying King Hamad as it approached British Prime Minister Theresa May's office for a visit.