By Martin Petty
HANOI (Reuters) - The United States expressed alarm over Vietnam's jailing of three activists on Tuesday for obstructing traffic, charges described by rights groups as trumped-up and aimed at crushing freedom of expression. A court in southern Dong Thap province found them guilty of "causing public disorder" and handed out sentences of between two and three years, the latest sign of Vietnam's zero-tolerance approach to dissent at a time when its communist rulers are seeking closer engagement with Western powers. Rights groups monitoring the one-day trial said the defendants, Bui Thi Minh Hang, Nguyen Thi Thuy Quynh and Nguyen Van Minh, had been arrested in February while riding in a convoy of motorcycles to visit a former political prisoner interrogated by police a day earlier.
"The use of public disorder laws by Vietnamese authorities to imprison government critics for peacefully expressing their political views is alarming," the U.S. embassy in Hanoi said in a statement late on Tuesday, urging the unconditional release of all political prisoners.
Free speech is enshrined in Vietnam's constitution but critics have been jailed for spreading "anti-state propaganda".
Four dissidents were released between April and June this year but Amnesty International says scores of others remain in detention for expressing their opinions in a country that was granted a seat last year on the U.N. Human Rights Council.
Amnesty also expressed concern over Tuesday's verdict and urged the government to "rein in its police and stop attacks on peaceful activists".
The jail terms are a setback for U.S. efforts to build stronger trade and military ties with Vietnam to offset the influence of its giant Communist neighbor China. Washington has offered broad incentives if Vietnam can show progress on human rights, including freedom of speech, assembly and worship.
Some U.S. Senators, including former presidential candidate John McCain, have said Vietnam has made sufficient improvements to secure bipartisan support in Washington to start lifting a 30-year-old arms embargo as early as next month, something Hanoi has long called for.
Hang, 50, the most prominent of the three dissidents, spent five months at a re-education facility in 2012 for her silent protests over the arrest of fellow activists, the New York-based Human Rights Watch (HRW) says.
Minh is a religious freedom campaigner and member of the Hoa Hao Buddhist sect, which is not authorized by the state.
HRW deputy Asia director Phil Robertson said the charges against the three were "bogus" and "outrageous".
"Bui Thi Minh Hang and her colleagues have been railroaded into prison for simply exercising their right to associate and assemble ... and for daring to use their voices to show solidarity with others facing persecution," Robertson said.
(Editing by Gareth Jones)