Vietnam has arrested a prominent dissident writer and blogger just hours after holding talks with the United States on human rights.
Pham Doan Trang was detained in Ho Chin Minh city late on Tuesday and accused of carrying out anti-state activities.
Ms Trang has been detained before and is an advocate for democracy, press freedom and the rule of law in Vietnam.
Vietnam’s one-party communist state frequently jails its critics. There was no immediate comment from the US.
Human Rights Watch and Amnesty International have demanded her immediate release.
Ms Trang has been charged with “making, storing, disseminating or propagandising information, materials and products that aim to oppose the State of the Socialist Republic of Vietnam”, state media report.
Such charges carrying jail terms of up to 20 years.
“There will be more arrests of dissidents and human rights activists before the Communist Party’s 13th Congress early next year,” fellow dissident Pham Thanh Nghien told BBC Vietnamese. “It turns out Doan Trang is first in line.”
Another activist, who did not wish to be named, told BBC Vietnamese: “Looking at the range and depth of Doan Trang’s activities in the past years, it is totally predictable that she would be detained. Trang was prepared mentally to go to prison.”
Earlier this year, Ms Trang stopped working for an independent book publisher, citing police harassment, heightened state abuse and the abduction of colleagues.
With the growing importance of social media, the internet has become a vital platform for dissidents in a country which tightly controls its press.
The 24th annual US-Vietnam Human Rights Dialogue was held for three hours on 6 October and “addressed a wide range of human rights issues”, the US state department said on its website.
“The promotion of human rights and fundamental freedoms remains a critical pillar of US foreign policy and is key to further building upon the US-Vietnam Comprehensive Partnership,” it added.