Police detained Bahraini human rights campaigner Maryam al-Khawaja after her arrival in the Gulf country on Saturday, her mother said.
Al-Khawaja has dual Bahraini and Danish citizenship. Her mother, Khadija al-Musawi, told The Associated Press that her daughter was refused entry after presenting her Danish passport and a Bahraini identification card, and at one point was surrounded by police.
The activist has said she wanted to visit her jailed father, Abdulhadi al-Khawaja, who is on hunger strike to protest his detention.
Lawyer Mohammed al-Jishi told the AP that prosecutors plan to press charges against al-Khawaja that include insulting the king and police. Bahraini authorities had no immediate comment.
The tiny island nation of Bahrain is a Western ally that hosts the U.S. Navy's 5th Fleet. It has faced more than three years of unrest from an opposition movement led by the country's Shiite majority that is seeking greater political rights from the Sunni monarchy.
In July, it ordered U.S. Assistant Secretary of State for Democracy, Human Rights and Labor Tom Malinowski to leave the country after he met with a leading Shiite opposition group, leading to a rift with Washington. U.S. State Department spokeswoman Jen Psaki earlier this week cited concerns about the "harassment and imprisonment of persons exercising their rights of freedom of expression" in the country.