The head of an outlawed pro-independence Basque party has been jailed by a judge who accused him of leading the armed separatist group ETA (search), but the man's associates said Thursday the action undermined efforts for peace.

The order against Arnaldo Otegi (search), the leader of the Batasuna party (search), which is seen as the political wing of ETA, came late Wednesday after a car bomb blamed on ETA injured 52 people in Madrid. Otegi has denied belonging to ETA.

Otegi's lawyer, Jone Goirizelaia, said the jailing was "revenge" for that blast, the sixth blamed on ETA since Spain offered the militant group peace talks if it renounces violence.

Another leading Batasuna member, Joseba Permach, said the Spanish government was behind the judge's order. He said it was tantamount to "slamming the door, an aggressive response to the desire for peace of the Basque country, not just Batasuna."

Before being jailed, Otegi was interrogated for three hours over an alleged ETA financing scheme. As he arrived to testify, a handful of protesters screamed "murderer" at him. Otegi looked right at them and gave a wry smile.

Another suspect, Jon Salaberria, who was also summoned to testify, failed to show up. A warrant for his arrest was issued.

Otegi left the courthouse in handcuffs and was driven to prison on the outskirts of Madrid.

In the jailing order, which stops short of a formal indictment, Judge Fernando Grande-Marlaska wrote that Otegi "holds a leadership position in the terrorist network" led by ETA. Otegi has denied the charge.

Batasuna members scrambled Thursday to come up with the $500,000 bail. They said they were opening a bank account for people to make donations.

Otegi, 47, has on many occasion has given statements as the prime spokesman for the Batasuna party, which the Spanish Supreme Court outlawed in 2003 on grounds that it is part of ETA, blamed for more than 800 death since the late 1960s.

Even after that ruling Otegi retained his seat in the Basque regional legislature. Judges could not prosecute him until now because he had immunity as a lawmaker.

But he lost this protection after April 17 elections in which Batasuna was barred from running, allowing judges to question and charge him.

Otegi is the most prominent and visible member of the militant pro-independence movement in the Basque country. He served six years in the late 1980s and early 1990s after being convicted of taking part in an ETA kidnapping.