Mr Dupuis wanted to lend his support

Mr Dupuis' colleague from the Italy-based Transnational Radical Party, Martin Schultes, said he wanted to offer his support to Mr Do.

A statement from the International Buddhist Information Bureau quoted Mr Dupuis as saying: "My presence here as a European citizen and TRP secretary general is an act of solidarity with all those ... in Vietnam who have struggled for decades for the establishment of the rule of law, democracy and fundamental freedoms."

US pressure

The US Government has called on Vietnam to release the detained monk and to allow people to practise their faith freely.

Mr Do is deputy head of the outlawed Unified Buddhist Church of Vietnam. The BBC Hanoi correspondent says Vietnam currently recognises six religious groups and other organisations face sustained harassment.

Thich Quang Do is a member of an outlawed Buddhist organisation

His detention comes as the US Congress is considering a key trade pact with Vietnam which is vital if the developing country is to meet growth targets planned for the next decade.

Some congressmen have raised concerns over Vietnam's poor record of respecting religious freedoms.

But Vietnam says that it does not think Mr Do's detention will jeopardise the treaty.