President Jacques Chirac (searchcalled a meeting of his top advisers Friday after raising France's terror alert level in response to the train bombings in Madrid (search).

The meeting was called "to examine the situation the day after the Madrid attacks and to assure the proper application" of heightened anti-terror measures, Chirac's office said.

Prime Minister Jean-Pierre Raffarin (searchattended the morning meeting with Interior Minister Nicolas Sarkozy, Defense Minister Michele Alliot-Marie, Foreign Minister Dominique de Villepin, Justice Minister Dominique Perben and Transportation Minister Dominique Bussereau.

Flags at public buildings in France were lowered to half staff, on Chirac's request, and would remain lowered for three days -- the period of Spain's national mourning. The attacks killed nearly 200 people and wounded over 1,400.

Raffarin's office said he would travel to Madrid and represent the French government at a rally Friday evening to be led by Spanish Prime Minister Jose Maria Aznar. Millions were expected to attend rallies around Spain. An evening vigil was planned in Paris at the Spanish Embassy.

France raised its color-coded terror alert late Thursday from yellow to orange, the second level in the four-level system. Raffarin's office said more soldiers would be patrolling trains and subways. Security also was stepped up along the France-Spain border.

The French Basque region has long been a haven for militant Spanish Basques, although it has largely been spared the violence that has scarred the Spanish Basque provinces, just across the border.

Spain thinks Basque separatists are behind the Madrid bombings but have not ruled out other possibilities, Foreign Minister Ana Palacio told French radio station RTL on Friday.

"All the objective elements that we have point to ETA," Palacio said in a telephone interview from Madrid.

The discovery of a stolen van with seven detonators and an Arabic-language tape, she said, was "an element that we have to study."

"Obviously, when we conduct an investigation we cannot exclude other possibilities."