Spanish Interior Minister Jose Antonio Alonso said "everything points to ETA" in the first attacks to hit the Spanish capital since the March 11 train bombings earlier this year, which killed 191 and injured nearly 2,000.

The low-intensity blasts went off at nearly the same time in the early evening shortly after a caller to the Basque newspaper Gara, claiming to represent the militant separatist group, warned the attacks were imminent.

Alonso told a news conference the bombs hit the gas stations along main roads leading out of the capital. The service stations were evacuated before the blasts, no one was hurt and there was no damage, he said.