Madrid - Spain's Supreme Court on Tuesday lifted prison sentences handed to 14 among a total of 20 Islamists who were convicted in February of membership or collaboration with cells planning attacks, including a scheme to blow up the main anti-terrorism court.

The National Court had sentenced the 14 to prison terms ranging from seven to 11 years for belonging to a terrorist organization.

The court confirmed the sentences handed to six others, but lowered one of them.

Algerian Redha Cherif was acquitted of belonging to a terrorist group, but the court maintained his verdict for falsifying documents, lowering his sentence from nine to two years.

Because Cherif has already been jailed for two years, he will now be released.

The court confirmed the 14-year sentence of Algerian cell-leader Mohammed Achraf, who was found to have tried to obtain explosives in order to blow up the National Court with a truck loaded with 500 kilogrammes of explosives in 2004.

No evidence was found, however, of clear plans or a firm decision to carry out the attack.

The Supreme Court also confirmed the jail terms of four others, who had been given between five and 10 years.

Achraf created an extremist cell in the prison near Salamanca where he was serving time for credit card fraud, proclaiming the need for suicide bombings, according to the National Court.

The cell wrote letters to inmates in other Spanish prisons, creating a network which represented a "serious danger" to Western and Spanish society, the court said.

In October 2007, the National Court convicted 21 people of involvement in the Madrid train bombings, which killed 191 people in March 2004.

Three of the convicts, who were found to have planted or helped to prepare the bombs, were handed jail terms of more than 30,000 years each. (dpa)