A police doctor scouring Nairobi’s Westgate mall for bodies after a four-day siege by Islamist gunmen that claimed dozens of lives has said victims were tortured before they died, according to a Kenyan newspaper.

“Those are not allegations. Those are f****** truths,” the doctor, a forensics expert, told The Star newspaper. “They removed balls, eyes, ears, nose. They get your hand and sharpen it like a pencil then they tell you to write your name with the blood. They drive knives inside a child’s body. Actually, if you look at all the bodies, unless those ones that were escaping, fingers are cut by pliers, the noses are ripped by pliers.”

The information could not be independently verified, but William Pike, the British editor of The Star, said the reporters working on the story had been given similar accounts from other sources. “We have [the source] on a recording,” Mr Pike said. “He was talking very graphically, and he was very angry.”

Download the new Independent Premium app Sharing the full story, not just the headlines

The horrifying details of what may be the last moments of some of the hostages at the hands of terrorists from Somalia’s al-Shabaab movement come amid mounting public anger over the authorities silence about the details of the siege. Many questions remain, such as what happened to the potentially dozens of hostages still unaccounted for? What happened to the attackers? And what caused parts of Westgate to collapse in the final hours of the siege?

Police have asked for patience as they begin the painstaking work of gathering evidence and searching for bodies, with Interior Minister Joseph Ole Lenku warning it could take up to a week to complete the search. He has said that an “insignificant” number of bodies are still trapped.

Gunmen armed with machine guns and grenades stormed the Westgate mall on Saturday lunchtime, shooting indiscriminately, and killing at least 61 people. A further six security officers died in attempts to rout the militants. During the siege, rescuers evacuated many survivors, but reports suggested hostages were being held by militants. Kenya’s Red Cross says that 71 people are still listed as missing.

Ghoulish accounts on the fate of the hostages have circulated Nairobi and there have been claims that the military was forced to blow up part of the Westgate complex not just to bring the siege to an end, but to end the appalling suffering of hostages amid reports that hostages were raped, and others beheaded and their heads thrown out of the windows.

None of these reports could be verified amid what is a febrile atmosphere in the city following the worst terrorist attack on Kenyan soil since the US embassy bombings by Al-Qa’ida in 1998 that killed more than 200.

Allegations of rape are not commonly linked with Islamist militants, although there are increasing numbers of rape cases reported in Somalia after long years of conflict.

Meanwhile, Kenyan authorities are also facing questions over whether they had any intelligence on an impending attack, which a Somali al-Shabaab chief said was a “message to Westerners” who had “backed Kenya’s invasion [of Somalia],” a reference to Kenya’s 2011 incursion aimed at crushing the militant movement.

Kenya’s National Intelligence Agency (NIS), widely accused by politicians of failing to pick up chatter about the attack, has insisted it did warn the police and officials inside the President’s office before the Westgate siege, but its warnings went unheeded, The Star reported.

According to the same report, a pregnant policewoman avoided Westgate after her brother, who works for Kenyan intelligence, warned her of a terror attack. “She has told police that her brother who is a NIS officer warned her not to visit Westgate that Saturday because she would not be able to run,” a senior officer was quoted as saying.