Jan. 5 (Bloomberg) -- Spain arrested 62 people last year in investigations into the March 11 train bombings in Madrid, raising the number of detentions for international terrorism to the level of suspected members of the domestic group ETA.

Of the 266 people arrested in terrorism probes, 131 had relations with Islamic and foreign groups, up from 34 the previous year, Interior Minister Jose Antonio Alonso said at a press conference in Madrid to review ministry work in 2004.

The rest were related to ETA, which had been the primary focus of the ministry for the assassinations of more than 800 people since the late 1960s in its campaign for a Basque state.

Detentions stemmed from cases that ranged from an Islamic extremist plot to bomb the Madrid-to-Seville high-speed railroad to what police called the take-down in France of ETA's top leadership.

Spain stepped up investigations of Islamic groups including al-Qaeda after the Sept. 11, 2001, attacks in the U.S. and the Madrid bombings, which killed 191 people and injured more than 1,500 in Spain's worst ever terror attack.

Forty-two people were arrested by Spanish security forces breaking up an Islamic group they said was planning to blow up monuments including Spain's National Court building, where terror suspects are investigated, Alonso said.

The 62 arrests in the March 11 bombings and related attacks helped unravel the plot behind the train attacks, the ministry said in a statement. The events include the high-speed railway incident, which was foiled before a bomb exploded, and the suicide bombing of seven suspects cornered by police.

Investigators have said there are links to al-Qaeda among some suspects jailed in connection with the March 11 bombings, which followed the Sept. 11 bombings by 911 days.

Responsibility for March 11 probably lies primarily with three groups of Islamists, whose members are mostly Moroccan nationals and who share the Salafist ideology, which advocates violence to enforce Islamic law, El Pais reported last month.

To contact the reporter on this story: Todd White in Madrid at at twhite2@bloomberg.net.

Last Updated: January 5, 2005 10:05 EST