Human Rights Watch said Tuesday that Truong Van Suong died Monday at Nam Ha prison outside Hanoi after being held for more than 33 years.

He is the second Vietnamese political prisoner to die behind bars since July.

Suong, 68, suffered from heart disease and high blood pressure.

A prison official declined to comment, and Vietnam's Foreign Ministry could not immediately be reached for comment.

Vietnamese political prisoner Nguyen Van Trai died in prison on July 11.

The Associated Press - September 13, 2011