Father Sergio Baldin, the Franciscan friar who is fighting for his life after being savagely attacked at a monastery in the foothills of the Alps near Turin, had recently enraged a local criminal gang by helping an Albanian prostitute to escape its clutches, church sources said today.

Colonel Antonio Di Vita, head of the Carabinieri in the province of Turin, said that although all options were open, the predominant police theory was that Father Baldin and three other monks, who were all badly beaten by three masked assailants, were the victims of an attempted robbery.

However Father Gabriele Trivellin, provincial head of the Franciscan order of Friars Minor, said that the "sheer fury" of the assault showed that the aim was not theft but revenge. He was backed by Cardinal Severino Poletto, the Archbishop of Turin, who said: "If you ask me if this was a punitive raid, I would say yes, the facts point in that direction".

Father Trivellin said that the monks, who are all being treated in hospital, were known to have had helped girls involved in local drugs and prostitution rackets to leave a life of crime and turn to religion. "I know that one young girl in particular recently presented herself at the monastery and asked for help," he said.

Church sources said that Father Baldin had given the girl — "the most beautiful of the prostitutes, the one customers most asked for" — spiritual instruction so that she could change her life. He had even accompanied her back to Albania.

He had been threatened on his return, and at the end of July and beginning of August there had been several minor thefts at the monastery which may have been reconnaissance trips by gang members. Corriere della Sera said that it appeared the monks had interfered with a profitable business run by a local gang that supplied girls and cocaine to wealthy clients for parties.

About 20 handwritten Post It notes appeared yesterday on the monastery gates accusing the monks of being "paedophile priests". One of the scrawled notes, which have since been removed by police, read "Vatican, paedophile priests, jail is not enough, beat them!". However police said that this could be either an attempt to lay a false trail for investigators or simply an "anti clerical" gesture.

Doctors said that the condition of one of the monks, Father Emanuele Battagliotti, 81, had worsened overnight. Father Baldin, 49, whose skull is fractured and who has undergone brain surgery to remove a blood clot, is still in a coma in an intensive care unit at a Turin hospital.

Father Baldin, Father Battagliotti, Father Salvatore Magliano, 86, and Father Martino Gurini, 76, a former missionary in Bolivia, were having their evening meal at the San Colombano Belmonte monastery near Turin when they were attacked by three hooded men who gagged and bound them before punching, kicking and beating them with clubs.

The attackers made no attempt to enter the monastery church, where a gold crown on a statue of the Madonna was stolen in 2006 but later recovered. It is now kept behind bullet-proof glass. Police said that the attackers took only a small amount of cash from the friars.

Davide Brunasso, the local mayor, said that Father Baldin was a "born organiser" who had revitalised Catholic activity in the local community after arriving at the monastery two years ago, especially among the young. Earlier Father Battagliotti, who was the first to be attacked after investigating a noise, testified that as one of the gang was beating Father Baldin with a club he heard him say in Italian "I'm going to kill you".

Italian media compared the attack to A Clockwork Orange, Anthony Burgess's story of violent young thugs, filmed in 1971 by Stanley Kubrick.