MADRID, March 12: Backpack bombs used in deadly Madrid train bombings were set off by mobile phone and contained copper detonators, which are not generally used by armed Basque separatist group ETA, a radio report said on Friday.

The report on private radio station Cadena Ser quoted security sources as saying the components may point to the bomb having been set by an extremist Islamic group such as Al Qaeda.

The report said the bombs, which blew up on four trains killing 198 people, were activated by mobile telephones that had had their alarms set for 7.39am (0639 GMT) on Thursday.

The detonator in an unexploded bomb recovered by police contained a copper detonator whereas the detonators commonly used by ETA are made of aluminium, the report said.

The backpack examined by investigators was picked up from one of the mangled trains and put together with other lost luggage after the blasts, Cadena Ser said.

It was later found to contain an unexploded bomb, which police defused, according to the report.

The backpack contained 10.2kgs of Spanish-made plastic explosives. The detonator was also Spanish-made.-Reuters