Rights activist and blogger Nguyen Ngoc Nhu Quynh, more commonly known as Me Nam which means "Mother Mushroom", was detained Monday as she visited a fellow dissident in jail in southern Nha Trang city.
Quynh, whose critical Facebook posts have included articles about civilians reportedly dying in police custody, was accused of distorting truth and history, defaming the Communist Party and provoking anti-state violence, according to the Ministry of Public Security's official newspaper.
Her arrest comes after the appeal trials of two other bloggers in recent weeks, one whose sentence was upheld and another whose prison term was reduced by one year.
"This trend threatens to overshadow Vietnam's progress on human rights," US Ambassador to Vietnam Ted Osius said in a statement Wednesday.
"The United States calls on Vietnam to release these individuals and all other prisoners of conscience, and to allow all individuals in Vietnam to express their political views online and offline without fear of retribution."
EU Ambassador Bruno Angelet also called for Quynh to be freed, saying in a statement Tuesday that her "arrest goes against Vietnam's international and domestic human rights obligations".
Last month, a Vietnamese court upheld prominent blogger Nguyen Huu Vinh's five-year sentence, as well as the three-year jail term of his assistant Nguyen Thi Minh Thuy.
Weeks later, 50-year-old blogger Nguyen Dinh Ngoc had his sentence reduced from four years to three.
