Swiss police revealed yesterday that Matthias Schepp, the father of missing Swiss six-year-old twins, told their mother he had killed the girls in a letter sent shortly before he committed suicide in southern Italy.

The revelation a week after his death came as dozens of French police combed one of his last stopovers, the Mediterranean island of Corsica, for traces of the daughters, including areas where Mr Schepp had visited on holidays in recent years.

Police, who have described the 43-year-old as a “desperate person” during his three-country dash last week, said that the last letter was post-marked the day he threw himself under a train.

“The last envelope dated February 3 contained a letter in which the father said he killed the two girls, saying he was in Cerignola (southern Italy) where he was about to kill himself,” Vaud regional police spokesman Jean-Christophe Sauterel told journalists.

“I can confirm that in his letter he also said that they did not suffer and were resting in peace,” he added.

“In all likelihood they are in Corsica,” said Mr Sauterel.

Investigators in Corsica were trying to piece together reported sightings of the fair-haired twins and their father on February 1, especially in Propriano where they arrived by ferry, sources close to the probe there said.

Police in Switzerland, France and Italy have been engaged in an increasingly gloomy hunt for clues about the fate and whereabouts of the girls after Mr Schepp failed to return them to his estranged wife in Switzerland on January 30.

Mr Schepp killed himself in Cerignola four days later, in apparent desperation at his separation from his wife Irina Lucidi and a custody dispute over the daughters.

Witnesses reported noticing the twins with their father on board a ferry between the southern French port of Marseille and Corsica, while Mr Schepp later returned to the French mainland apparently alone before heading to Italy.

Investigators found after examining his computer that Mr Schepp had consulted websites on suicide, poisoning and firearms as well as travel to Corsica before his turn for custody of the girls.

“We are dealing with someone who was extremely meticulous and who planned a certain number of things, including his trip to Corsica,” Mr Sauterel told journalists late Thursday.

The last letter was among eight envelopes from southeastern Italy that Swiss police learned about three days ago but kept under wraps with the family’s agreement.

The rest contained €4,400 in cash, while another €1,500 was found by Italian police in a disused letter box, said Mr Sauterel.

Lucidi’s family have said Mr Schepp suffered from a split personality.

Swiss newspaper 24 Heures reported that he had been receiving psychiatric counselling, although there were no signs he presented a danger for his daughters. By all accounts Mr Schepp was regarded as a loving and doting father before his fateful trip.

Mr Schepp’s parents and siblings spoke for the first time of their “great distress and worry” at his “terrible” actions.

“We all agree and are persuaded that our brother could have committed in recent times acts that are so terrible due only to a serious mental disorder and the loss of his normal personality,” they said in a statement to the Swiss news agency ATS.

“We have all suffered because of his death and the terrible and uncertain fate of our two nieces and granddaughters.”

The distraught mother, Irina Lucidi, left her home in the western Swiss lakeside village of St-Sulpice on Thursday, as both sides of the family asked not to be disturbed.