Tributes to Giap, whose guerrilla tactics defeated the French and US armies, flooded cyberspace soon after his death at 102 on Friday. But reporters in some of the biggest state media outlets could not print a thing about the biggest event in years.
"It's really stupid -- but we can't do what we want. It's just procedure we have to follow," one disgruntled editor at a top state-run news agency told AFP, adding that outlets had to wait for an official announcement -- which was not released until yesterday.
A delay between the death of a top public figure and a formal announcement is standard practice in authoritarian Vietnam.
But social media is increasingly filling the country's information void, despite crackdowns on online dissent that have seen dozens of bloggers jailed.
"I learned the news of Giap's death from the internet," said Do Tuan Khai, 55, who owns a coffee shop in Hanoi.
Branded an "enemy of the Internet" by Reporters Without Borders, Vietnam bans private media while all newspapers and television channels are state-run.
Vietnam has also recently passed a sweeping new Internet law which bans bloggers and social media users from sharing news stories online, although it remains unclear how this will be implemented.
But the rise of blogs and social media means it will be harder for the communist party to control the official narrative around Giap as the country prepares for his funeral on October 13, Vietnam expert Carl Thayer told AFP.
"Then there will be the sore tale of a general... Who was shunted aside," which will not feature in the official narrative, he added.
Giap, who masterminded the French defeat at Dien Bien Phu and pushed the Americans out two decades later with the fall of Saigon, enjoyed near mythical status overseas as a master strategist.
But his success on the battlefield earned him powerful enemies at home, and he was pushed to the political sidelines after Vietnam's reunification in 1975.