The court in Binh Thuan province handed down prison sentences of between two and two and a half years for “disturbing public order”, the Ministry of Public Security said in a statement on its website.

The six hurled bottles, bricks and petrol bombs at police during the protests on June 11, according to the statement.

Their lawyers were not immediately available for comment.

The protests, by thousands of people in several cities, were fuelled by concerns that a draft law to develop economic zones offering land leases of up to 99 years would be dominated by investors from China, a neighbour with which Vietnam has a rocky history.

Police have detained dozens of people following the protests, including in the economic hub of Ho Chi Minh City and the capital, Hanoi.

Last month, police in Ho Chi Minh City issued a prosecution order for an American man of Vietnamese descent for his alleged involvement in the protests.

US Secretary of State Mike Pompeo raised the issue of Will Nguyen during his meetings with Vietnamese officials in Hanoi this week, encouraging a speedy resolution.

The police statement said the convicted six had admitted guilt during the one-day trial.