Counterterrorism police officers yesterday intensified their search for leads to the perpetrators who planted a pipe bomb that killed an Afghan boy in Kato Patissia on Sunday night after terrorist guerrilla group the Conspiracy of the Cells of Fire denied any link to the blast and two claims of responsibility were dismissed as hoaxes. Meanwhile, doctors at the Athens hospital treating the dead boy’s 10-year-old sister, whose eyes were injured by shrapnel from the bomb, said the girl would undergo another operation today. Police said they were not treating as serious a phone call made to Kathimerini shortly before noon yesterday by an unidentified man who said an unknown organization called the «Lambros Fountas Guerrilla Group» had been behind Sunday’s blast. Fountas was a 35-year-old suspected terrorist killed in a shootout in southeast Athens earlier this month. The fact that the call to Kathimerini was not followed by a written proclamation and that the caller warned of forthcoming hits raised the suspicions of police. Counterterrorism officers were also unconvinced by a written claim of responsibility uploaded onto the Internet by another previously unknown group calling itself the Revolutionary National Socialist Front. Forensic experts said Sunday’s pipe bomb had comprised the same slow-burning explosive as that used in last weekend’s bomb blast at the central Athens offices of the extreme-right organization Chrysi Avgi (Golden Dawn), an attack claimed by the Conspiracy of the Cells of Fire. Sunday’s device also resembled a bomb used in an attack on the Chilean Consulate in Thessaloniki in July, claimed by the same group. Citizens’ Protection Minister Michalis Chrysochoidis said he was «determined to deliver a strong response to terrorists and common criminals.» Meanwhile the leader of conservative opposition New Democracy, Antonis Samaras, visited the police station in Patissia, near the spot of Sunday’s blast. «This can’t go on any longer,» Samaras said, referring to the recent spike in domestic terrorism.