Spanish officials say at least 131 people have been killed and hundreds more wounded in several near-simultaneous explosions on commuter trains in the capital, Madrid.
The blasts occurred early Thursday during the busy morning rush hour on trains at or near three stations, including the main train station (Atocha) in the southern part of the city.
There has been no claim of responsibility, but police say they suspect the blasts -- just days ahead of Sunday's general elections -- may be the work of the armed Basque separatist group, ETA.
Interior Minister Angel Acebes says there was no warning to authorities before the explosions. ETA often calls in warnings before carrying out bombings. However, terrorism linked to Spain's cooperation with the U.S. led war in Iraq has not been ruled out.
All campaigning for Spain's election has been called off, and the French News Agency says Prime Minister Jose Maria Aznar has declared three days of mourning for the victims.
Britain, France and Germany, the Vatican, and the United Nations have condemned Thursday's bombings.
If ETA is responsible for today's attack it would be the deadliest ever carried out by the group. In 1987, an ETA bombing of a supermarket in Barcelona killed 21 people.
More than 800 people have been killed in ETA's 35-year armed campaign for an independent Basque state in northern Spain and southern France.
The Spanish government refuses to negotiate with ETA, which both the United States and the European Union have branded a terrorist group.
Some information for this report provided by AP, AFP and Reuters.