Bahraini authorities arrested four Americans during protests marking the fifth anniversary of the peaceful revolution in the kingdom, US and Bahraini authorities said Monday, drawing condemnation from rights groups.

Bahraini authorities arrested four Americans during protests marking the fifth anniversary of the peaceful revolution in the kingdom, US and Bahraini authorities said Monday, drawing condemnation from rights groups.

They include an independent journalist named Anna Therese Day and three members of her camera crew, according to a statement issued by Day's family.

Bahraini police said four Americans, among them a woman, were arrested around the town of Sitra on Sunday during clashes between security forces and protesters, in a statement published by the official Bahrain News Agency.

"Some of those arrested had carried out journalistic activities without permission from concerned authorities, in addition to carrying out illegal acts," the statement read, without clarifying the nature of these acts.

Day's family said the four were committed journalists and denied they had done anything wrong, calling for their immediate release.

"The allegation that they were in any way involved in illegal behavior or anything other than journalistic activities is impossible," a spokesperson for the family said in a statement.

The US State Department said it was aware of reports that Americans had been arrested in Bahrain but declined to comment further, citing privacy concerns.

Rights groups also criticized their detention, with the New York-based Committee to Protect Journalists branding Bahrain "one of the worst jailers of journalists in the Arab world".

"It is sad that the fifth anniversary of the protests is marked by the arrest of yet more journalists in Bahrain," said Middle East and North Africa program coordinator Sherif Mansour.

Activist Brian Dooley from Human Rights First called the arrests "another alarming reminder of how dangerous Bahrain is for reporters," urging Washington to "stand up to its repressive military ally".

Day is an award-winning journalist who has reported extensively from the Middle East, North Africa and elsewhere, and her work has been featured in news outlets including the New York Times and CNN.

Bahrain said the case of the four detainees has been referred to the public prosecution.

Home to the US Fifth Fleet, Bahrain was rocked by a peaceful Arab Spring-inspired uprising demanding social reforms, social justice and a constitutional monarchy on February 14, 2011.