ATHENS // Gunmen shot dead an anti-terrorist police officer guarding a witness in central Athens early today, in an escalation of domestic terrorist attacks in the country. Police spokesman Panagiotis Stathis said between 15 and 20 shots were fired at the officer by at least three gunmen at about 6.20am in the residential district of Patisia. "There was no warning, no telephone calls," Mr Stathis said. "This was a cold-blooded murder." It was the first targeted killing attributed to domestic terrorism in years. Greek domestic terrorist groups have stepped up attacks, particularly against police targets, since the country was struck by massive riots in December triggered by the fatal police shooting of a teenage boy. But most have been late-night bombings that have caused no injuries. "From one minute to the next, after the events of December, the police was suddenly on the ropes, in a situation where all of its actions were viewed in a negative context," Mr Stathis said. "These people will be caught and brought to justice." The officer had just taken over the morning shift of guard duty outside the home of a key witness in the trial of the far-left Greek terrorist group Revolutionary Popular Struggle, known by its Greek acronym ELA. Only the officer was targeted in the attack, with no apparent attempt to approach the witness' home. The coroner Philippos Koutsaftis said the officer had died of multiple gunshot wounds to the body and head. "He was carrying a gun which was holstered. He was hit many times by shots that appear to have been fired at close range," he said. Before disbanding in 1995, ELA was blamed for killing a police officer and a Supreme Court prosecutor, as well as scores of bombings over 20 years. More than 30 attacks were aimed at American targets, mostly in the early 1980s, including the bombing of the US ambassador's residence, embassy vehicles, and branches of American banks and companies. * AP