Romanian prosecutors have detained a member of Hungarian ultra-nationalist group HVIM suspected of intending to detonate an explosive device in the Transylvanian town of Targu Secuiesc during yesterday's national day celebrations.

More than one million ethnic Hungarians live in Romania, mostly in three counties in central Transylvania, a territory at the foot of the Carpathian mountains that was run by Budapest until 1918 but is now far from the Hungarian border.

HVIM is an ultra-nationalist group that seeks a "Greater Hungary" and it has a Romanian unit. Targu Secuiesc is a small town in Covasna county full of pastel-shaded houses known as Kezdivasarhely in Hungarian.

Prosecutors from the DIICOT anti-organised crime and terrorism unit said on Tuesday they had taken a suspect into custody, but did not give his name.