Sicily Hit by a Surge in Mafia Violence : Crime: There have been nine killings in the past 10 days. Investigators believe most of the slayings are tied to defections.

Mafia killers are back on the streets of Sicily, jostling for power, settling old scores and attacking new enemies who have broken the Cosa Nostra code of silence.

Four new slayings brought to nine Tuesday the number of Mafia killings on the island in the last 10 days.

“There may be worse to come. We must stop this machine of death,” said Roberto Scarpinato, a deputy prosecutor in Palermo.

Police believe that some of the slayings are part of a struggle for power among Mafia clans after two years of quiet. But most of the killings, investigators believe, are aimed at a growing procession of defectors who have handed Mafia secrets to investigators.

“Part of this Mafia war is a struggle between a new generation and old leaders trying to hang on,” said Luciano Violante, the retired head of the anti-Mafia commission in Parliament.

In Palermo on Monday, two gunmen on a motorcycle assassinated Domenico Buscetta, 45, a jeweler and nephew of renegade Mafia boss Tommaso Buscetta. It was an act of vengeance and a warning to potential turncoats, officials said.

In 1984, Tommaso Buscetta became the first Mafia boss to violate omerta, the Mafia code of silence. He is still talking, and his nephew was Buscetta’s 12th relative slain in retribution.

Also Monday, in a suburb of Catania, three men were gunned down in the main piazza. Two had Mafia connections, police said. The third could have been a passerby who saw too much.

“They are using terror to pay old bills and to try to discourage new defections,” said Arnaldo La Barbera, the police chief in Palermo.

Since Tommaso Buscetta, now 67 and living under federal protection in the United States, broke the taboo, more than 1,000 Mafiosi have agreed to talk to judges and police. They are known as pentiti , the penitent ones.

Buscetta’s testimony alone to Judge Giovanni Falcone--who was killed by Mafia bombers in 1992--helped convict 338 Mafiosi at a huge trial in 1987.

More recently, Buscetta is among pentiti who have accused former Prime Minister Giulio Andreotti of consorting with the Mafia.

On Thursday, Marcello Grado, 23, was shot dead in a Palermo fruit market. Grado was a distant cousin of Salvatore Contorno, a mob killer turned pentito whose revelations have also brought numerous arrests.

Police say that nearly two dozen of Contorno’s relatives have been killed since he began talking in the mid-1980s. Contorno, 53, also now lives in the United States.

Sicily, birthplace of the Cosa Nostra, has been fairly quiet since the arrest two years ago of Salvatore (Toto) Riina, the long-sought Mafia boss of bosses.

Both Buscetta and Contorno, losers in an early 1980s struggle for power with Riina, have testified extensively against him.

New violence against their families comes as trials are beginning in Sicily and Rome against Riina and scores of other Mafiosi. Many of them, like Riina, are already jailed on other charges.

Testimony by pentiti is vital to the prosecution in Mafia cases and in unraveling a savage litany of its crimes in past decades.

Amid swelling violence, investigators insist that the tide is running against the Mafia and that the number of pentiti is accelerating.