A Vietnamese court convicted three prominent bloggers and sentenced them to between four and 12 years in prison, the latest step in a crackdown against online dissent in the tightly policed communist state.

One of the defendants' lawyers, Ha Huy Son, said the three bloggers were found guilty of writing articles that opposed the government, diplomats said. Monday's verdict came after a one-day trial in Ho Chi Minh City.

Vietnam's...