Truong Chau Huu Danh, 38, will be detained for three months as he is investigated for abusing democratic freedoms and infringing upon the interests of the State and lawful rights and interests of organizations and/or citizens, Can Tho police said.

Numerous documents relevant to the case have been seized by the police from Danh’s residence in the delta's Long An Province. Danh and his wife have been renting the house for several years.

Danh used to work for several local newspapers. Over the last five years, he has become well known for his Facebook posts on "whistle blowing" and his protests against toll booths of build-operate-transfer (BOT) projects in HCMC and other provinces.

However, some of his actions have been deemed illegal.

If Danh is prosecuted and found guilty, he could be jailed for up to seven years.