Israeli forces have joined Kenyan troops in the effort to save hostages from al-Qaida-linked Somali terrorists at a Nairobi mall where gunmen killed at least 59 people on Saturday, AFP reported on Sunday."The Israelis have just entered and they are rescuing the hostages and the injured," AFP quoted a security source as saying.The Jerusalem Post could not confirm the veracity of the report.Reuters quoted an Israeli security source as saying Israeli advisers were helping Kenya with "negotiating strategy" to help end the siege."There are Israeli advisers helping with the negotiatingstrategy, but no Israelis involved in any imminent stormingoperation," said the source, who gave no further details andasked not to be identified.The source said only a "handful" of Israelis, "purely in an advisory role", were on scene at the upscale Westgate shopping center, which has several Israeli-owned outlets and is frequented by expatriates and Kenyans.An Israeli source in Nairobi said all Israelis who were in the mall at the time of the attack had made it out safely, with the last three rescued overnight.There were conflicting reports from other security sources in Nairobi about the part Israel was playing.One Kenyan security source, who asked not to be identified, told Reuters that the Israeli military was involved in the operation, while a private security official also said they were helping comb the mall.But Kenyan Interior Minister Joseph Ole Lenku insisted it was a national operation, despite offers of foreign support.Lenku said Sunday that an unknown number of hostages remained in the mall, held by an estimated 10-15 gunmen.Earlier on Sunday gunfire erupted at the mall, lasting about 30 seconds after a period of tense quiet.Shortly after the shots were fired, troops in camouflage ran crouching below a restaurant terrace along the front of the building that had been buzzing with customers when assailants charged in. One witness said they first told Muslims to leave.Al Shabaab, the al-Qaida-linked group that claimed the attack, which is battling Kenyan and other African peacekeepers in Somalia, had repeatedly threatened attacks in Kenya if Nairobi did not pull its troops out of their country.President Shimon Peres sent a letter of condolence to President Uhuru Kenyatta of Kenya expressing sorrow at the needless loss of life in the horrific terror attack on the Nairobi shopping mall. In offering his prayers for the release of the hostages and the full recovery of the injured, Peres also conveyed his sympathy to the families of the victims. Peres termed terrorism to be a global threat stating those who perpetrate it make no distinction between young and old, men and women. "There is no justification for the murder of innocent civilians" he wrote, assuring Kenyatta that "Israel stands shoulder to shoulder with the Kenyan government and people at this difficult time." Peres noted that "we in Israel know the pain of terror and will do whatever we can to support the people of Kenya."In a statement released by President's office, Peres declared that terrorists are killing not only innocent people but innocent countries. "They are destroying country after country and they don't care about the extent of the damage" he stated. "It's a phenomenon that we now see at its peak, but not at its end." Peres urged all countries of the world to immediately take effective action to quell terrorist operations.