Quan is a Roman Catholic and the protesters included at least one member of the clergy, as well as elderly men and women.
Quan, in his early 40s, was detained in 2007 for three months on his return from a U.S. government-funded fellowship in Washington. He is one of Vietnam's better-known dissidents and maintains a popular blog that highlighted human rights abuses and other issues off-limits to the state media.
Vietnam converted to a market economy in the late 1980s and wants to integrate with the world, but maintains strict controls on freedom of speech and political expression. Bloggers, activists and others are routinely arrested and imprisoned. Foreign media representatives are allowed to live in Vietnam but are subject to restrictions on where they can travel and what they can report.
The Internet has emerged as a vital organizing tool for dissidents in recent years, and there has been a surge of blogs and Facebook pages highlighting criticism of the government. The rise of the Internet, combined with an economic slowdown, has left the ruling elite feeling vulnerable.