It emerged yesterday that two anonymous telephone calls on Wednesday morning ahead of explosions at the Athens Exchange in the capital and outside the Macedonia-Thrace Ministry in Thessaloniki had been made from the same cell phone in the center of Athens.

The discovery would appear to confirm police suspicions that the group behind the car bomb that detonated outside the Athens bourse and that behind the blast in Thessaloniki are either one and the same or in close collaboration. But police avoided connecting the two attacks yesterday.

Meanwhile, laboratory tests were under way on the remnants of the device that caused severe damage to the premises of the Athens Exchange in the central district of Votanikos and injured one person. It is thought that the results of the tests will confirm that the bomb had comprised ammonium nitrate, ammonium dynamite and petrol – a similar mix to the one the terror group Revolutionary Struggle had concocted and set in a car outside Citibank’s headquarters in February but which failed to go off.

After the Athens bomb detonated on Wednesday, a police spokesman had said the methodology of the attack “pointed to Revolutionary Struggle.” But yesterday police officials were more cautious about identifying the likely perpetrators of the attack, which had yet to be claimed by late last night. “We cannot even say whether the device was timer-operated, as we found no indications to prove this in the wreckage,” one officer said.