Around 180 people were arrested and four injured in Paris on Monday during an unauthorised protest by Tamils that turned violent, a police spokesman said.

Expatriate Tamils have been demonstrating around the world against the Sri Lankan government's conduct of the war against Tamil Tiger rebels. London has been a focus as many Tamils blame Britain, the former colonial power, for denying them a homeland.

Protesters blocked traffic at a junction in northern Paris and threw objects at three buses and police, the spokesman said, adding that four people were slightly injured, including one policeman.

Police described the gathering as an "armed crowd", a term generally used for groups carrying knives, guns or improvised weapons such as metal bars.