A crackdown on communist Vietnam's increasingly vocal dissidents has become the biggest in years, and activists say that authorities have been emboldened by the Trump administration's lack of emphasis on human rights.

U.S. President Donald Trump's decision to drop the Trans-Pacific Partnership trade deal also removed a clear incentive for Hanoi to show a better rights record, they said.

However, the U.S. State Department says it continues to insist that better ties will depend on Hanoi's progress on rights.