MADRID, March 13: Spain's intelligence service is "99 percent certain" that radical Muslims and not the Basque separatist group ETA are responsible for train bombings that killed 200 people, a Spanish radio station said on Saturday.

Private radio SER, whose owners have links to the opposition Socialist Party, said the National Intelligence Centre (CNI) believes the evidence points to a Muslim group, and that 10 to 15 people left bombs on the trains and fled, the radio said.

"The evidence has wiped out previous indications that led us to believe in ETA," the radio quoted one of its sources as saying.

Who was responsible is seen by political analysts as an important question that has a bearing on Sunday's general election.

Interior Minister Angel Acebes said at a press conference: "If it (is believed to be) Al Qaeda, no authorities from the state security forces have told me." A defence ministry spokesman declined comment on the radio report.

Many analysts say any proven ETA involvement in the bombings would probably benefit the ruling party because of its tough anti-ETA stance, but if the attack was the work of Muslim militants, it could be viewed as the consequence of Spain's domestically unpopular backing of the invasion of Iraq.

Cadena SER, citing high-ranking intelligence officials, said that at first ETA was suspected. That changed after police later on the day of Thursday's attacks discovered a stolen van near the railway station where three of the four bombed trains originated.

In that van were found seven detonators and, according to an eyewitness, an Arabic-language audio tape. The van did not have the false licence plates ETA normally attaches to its stolen vehicles.

Moreover, other evidence has pointed away from ETA, such as the type of detonators used and the synchronised nature of the attacks.

Four early morning trains were bombed at the same time, similar to the hijacking of four early morning commercial flights in the attacks of Sept 11, 2001, in the United States.-Reuters