WASHINGTON (Reuters) - Two decisions by Vietnamese courts sentencing a land rights activist to jail and upholding prison terms for two political bloggers are a concern for the United States, the U.S. State Department said on Monday.

"The use of criminal provisions by Vietnamese authorities to penalize individuals for exercising their right to freedom of expression ... is ... troubling," spokesman Mark Toner said at a daily news briefing.

Well-known Vietnamese political blogger Nguyen Huu Vinh, 60, and his assistant, Nguyen Thi Minh Thuy, 36, lost their appeal on Thursday when a higher court upheld their jail terms and reaffirmed they had abused their freedom and hurt the state's interests.

The five-year term for Vinh and the three-year term for Thuy were handed down in March and human rights and press freedom advocates have called for their release.

On Tuesday, a district court in Hanoi sentenced Can Thi Theu to 20 months in jail for causing public disorder, her lawyer said, jailing the land rights activist for a second time over a similar offense in a case a top human rights group said should have been dropped.

Theu, 54, was found guilty at a half-day trial three months after she was arrested for leading protests outside government offices against what she called illegal land seizures.

"We call on the government to release these three individuals as well as other prisoners of conscience and allow all individuals in Vietnam to express their political views and to assemble peacefully without fear of retribution," Toner said.

(Reporting by Arshad Mohammed; Writing by Mohammad Zargham; Editing by Sandra Maler)