Spain's parliamentary commission investigating the bombings of four rush-hour trains in Madrid on March 11 announced Wednesday that it would question former prime minister Jose Maria Aznar.

The pressure to call Aznar rose to a peak this week when Prime Minister Jose Luis Rodriguez Zapatero expressed interest in hearing his predecessor's testimony, contradicting his own Socialist Workers' Party, which had repeatedly said there was no need for Aznar to appear.

Aznar has expressed his willingness to appear before the commission since the probe got underway in June.

Critics of the commission accuse it of allowing partisan politics to mire the investigation as each of Spain's two main parties seeks to use the inquiry to absolve itself of any misconduct in connection with the bombings. Nearly 200 people died in the attacks, which authorities tentatively blamed on Muslim radicals.

Aznar's Popular Party government was unseated by Zapatero's Socialists in elections held three days after the attack.

A spokesman for the Popular Party, Eduardo Zaplana, said that his organization had unsuccessfully requested that Zapatero, newspaper editors, journalists and police informers appear before the commission.

The commission agreed to call 14 witnesses and to request 105 documents from various entities, including Interpol.

Also Wednesday, police arrested 10 people in Barcelona suspected of having provided logistical support to Muslim terrorists outside of Spain. Most were Pakistani nationals.

-- Pamela Rolfe