The leader of banned Basque separatist party Batasuna has been arrested in northern Spain.
Arnaldo Otegi is one of the most prominent Basque separatists
Arnaldo Otegi's arrest comes only three days after Basque militant group Eta, which is closely linked to Batasuna, called off its ceasefire.
It also follows a Supreme Court ruling confirming a 15-month prison sentence against Otegi for glorifying terrorism.
The arrest happened as Otegi, one of Basque separatism's leading figures, was due to give a news conference.
The Associated Press cited a court official saying Otegi had been detained in order to start serving his sentence.
He was being transferred to prison, the official said.
Otegi was sentenced last year for comments he made at a demonstration in 2003 marking the 25th anniversary of the death of an Eta rebel.
He appealed against the conviction, but a panel of judges unanimously rejected the appeal on Friday and his arrest followed swiftly.