Imprisoned Vietnamese blogger said to be weak after 29-day hunger strike

Human Rights Watch says it is concerned about the health of a prominent jailed Vietnamese dissident who has been on a hunger strike for 29 days.

Nguyen Van Hai, also known as Dieu Cay, is serving a 12-year prison term for conducting "propaganda against the state" in relation to his blogging and citizen media activities.

The human rights group quoted Hai's son as saying his father was too weak to walk unaided when he was allowed to visit him for five minutes in prison on Saturday.

Authorities were not immediately available for comment.

Hai is one of Vietnam's most celebrated dissidents. American President Barack Obama has raised his case publicly.

Later this week, Obama will meet Vietnam President Truong Tan Sang at the White House.