Bahrain Mirror (AFP): Bahraini authorities have arrested four Americans during protests marking the fifth anniversary of a Shiite-led uprising in the kingdom, US and Bahraini authorities said, 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.

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

"One of them was masked and taking part with a group of saboteurs in Sitra in acts of rioting and sabotage and attacks on security officials," it said. "The other three were arrested at a security checkpoint in the same area."

The four entered Bahrain between February 11 and 12 and "provided false information to concerned authorities" claiming to be tourists, police said.

"Some of those arrested had carried out journalistic activities without permission from concerned authorities, in addition to carrying out illegal acts."

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.

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 behaviour or anything other than journalistic activities is impossible," a spokesperson for the family said in a statement.

Rights groups also criticised 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 programme 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 an Arab Spring-inspired uprising demanding reforms and a constitutional monarchy on February 14, 2011.

Authorities crushed the protest movement one month later, but demonstrators have still taken to the streets and clash with police in Shiite towns surrounding Manama.