A Bosnian (search) man wanted for questioning in the Madrid (search) bombings voluntarily returned to Spain from what he called a vacation in Sweden and was arrested, the Interior Ministry said Saturday.

Sanel Sjekirica, 23, was arrested Friday night after he arrived at Madrid's Barajas airport on a flight from Stockholm, a ministry official said.

Sjekirica, who studies computer science in the northern Spanish city of Oviedo, told The Associated Press earlier this week in Sweden that he learned through media reports that he was a suspect.

He denied any role in the attack that killed 191 people, but said he once shared an apartment with Serhane Ben Abdelmajid Fakhet (search), the Tunisian real estate agent that Spanish authorities have identified as the ringleader of the plot.

The government says Fakhet was among seven terror suspects who blew themselves up in an apartment south of Madrid on April 3 as special forces prepared to storm it and arrest them.

Eighteen people have been charged in the attacks — six with mass murder and the rest with belonging to or collaborating with a terrorist organization. Fourteen are Moroccan. The others are two Indians, one Syrian and one Spaniard.

The charges do not amount to a formal indictment and do not necessarily mean they will stand trial.

On Friday the Interior Ministry announced the arrests of three more suspects — a Saudi citizen, an Egyptian and a Moroccan — for their possible links with other suspects.