Vietnam's authoritarian rulers typically move swiftly to muzzle critics and dissidents posting their opinions on social media.
Can Thi Theu -- who has already served two prison sentences -- and her son are believed to have been the first to spread news on social media about a clash between police and local residents in a village on the outskirts of Hanoi, in January 2020, in which three policemen and a resident were killed.
Villagers there had been resisting the military's attempts to build an airport on their land.
At a one-day trial in northern Hoa Binh province, Theu and her 32-year-old son Trinh Ba Tu were jailed for eight years for "spreading information against the communist state," said lawyer Dang Dinh Manh.
"Both defendants were strong at the trial today and although they admitted the acts that they did, they don't think what they did was wrong," he said, adding that both defendants would appeal.
Theu's older son Trinh Ba Phuong and another relative, who were arrested in June last year together with the other family members, will face trial at a later date.
Land disputes are common in Vietnam, where powerful individuals and companies often make claims on property.
"This conviction is a travesty of justice," said Emerlynne Gil, Amnesty International's deputy regional director for research.
"They are clearly being punished in retaliation for their peaceful activism to expose injustices and human rights violations."
The government, headed by Prime Minister Pham Minh Chinh, a former deputy head of the Public Security Ministry, strictly controls freedom of expression and the right to protest, but flashpoints occur.
A former reporter of a state-run newspaper was jailed for eight years on the same charge at a trial in April in the south east province of Phu Yen.
Tran Thi Tuyet Dieu was found guilty of posting stories and videos on Facebook and YouTube on subjects such as corruption, environmental pollution, and human rights.
According to Reporters Without Borders, Vietnam is ranked 175th out of 180 countries in the 2021 World Press Freedom Index. - AFP