An army commander in eastern Democratic Republic of Congo has been accused of leading the recent mass rape of at least 50 women. One of the victims, as well as sources quoted in a UN report, all accuse Lt Col Kibibi Mutware of links to New Year's Day rapes in the town of Fizi. There have been numerous cases of mass rape in DR Congo's conflict but this is believed to be the largest single incident allegedly involving the army. Lt. Col Kibibi has denied the charges. He said that the soldiers who raided the town had disobeyed orders. From an everyday fight between two men over a woman, violence escalated into a brutal punitive expedition by a group of government troops against the population of Fizi. "A soldier was killed here right beside the hospital," explains Dr Faise Chacha, the head of Fizi hospital. "That started the panic and all our patients fled. We came back at 0500 the next morning and we started taking in people who had been stabbed and others - women - who had been raped." Dr Chacha and the medical charity Medecins Sans Frontieres have treated 51 rape victims so far, but they expect more as women who fled the attacks slowly return home. As in previous cases of rape in DR Congo, many victims are expected to keep their plight secret to avoid being abandoned by their husbands and families. Two of them agreed to talk anonymously after medics told the BBC they had been raped. "I was raped in front of my four children," one of them told the BBC. "I'm ashamed, very ashamed. If I meet two or three people who are having a discussion, I assume they are talking about me, even though it is not the case." The other woman was able to identify her attackers. "It was 1900 [in the evening] and those who raped me were members of the military," she said in a low voice, her body wrapped in a colourful cloth. "There were four of them - Kibibi and his bodyguards. They stole all our belongings and our money." This woman was not the only one accusing Lt Col Kibibi, current commander of the 43rd sector in the army's Amani Leo (Peace Today) operation against rebel groups which still roam eastern DR Congo eight years after the country's war officially ended. Several people who live near the hospital said they saw him ordering his troops to attack the population to avenge their dead comrade. An internal report by investigators sent to Fizi by the UN peacekeeping mission Monusco and seen by the BBC also quotes local leaders and police sources who accuse Lt Col Kibibi of directing the atrocity. Monusco sent patrols from the day after the violence from its Baraka base, just over one hour's drive away, and has maintained a 24-hour presence in Fizi since 5 January, which has encouraged the population to come back. Lt Col Kibibi is a strong man with a small moustache and a boonie hat. When I met him, he was sitting behind a table on which only two mobile phones and one walkie-talkie were visible. Speaking in the thatched hut from which he commands his troops, he dismissed all accusations levelled against him as rumours and said that those soldiers who committed the crimes had disobeyed his orders to stay in the camp. He added that he only left his base briefly on 1 January to assess the death of the lynched soldier, and only heard about the night's violence the next morning. Lt Col Vianney Kazarama, the army spokesman for operations in South Kivu province, acknowledged that government soldiers were responsible for the Fizi attack but he promised swift legal action. "All those people who have abused the population have already been arrested. The zero-tolerance policy will be enforced on the spot in Fizi," he told the BBC. In a statement, the UN's special representative on sexual violence, Margot Wallstrom, called on the Congolese authorities to conduct an investigation "thoroughly and without delay". "Impunity for these types of crimes must not be tolerated," she added. Lt Col Kibibi is a former member of the CNDP rebel group, which has previously been accused of numerous human rights abuses. He was integrated into the national army as part of a peace agreement in 2009. According to a local military source, his unit is a mixture of former militias based on Rwandan-speaking ethnic groups. Those troops were deployed to Fizi where a conflict between the majority Babembe group and the neighbouring Banyamulenge - another Rwandan-speaking ethnic group - had been simmering for generations. Fizi residents and soldiers also clashed in April 2010. The 16 years of unrest in eastern DR Congo have become notorious for the widespread sexual abuse of women and young girls. More than 300 women, men and children were raped by a coalition of rebel groups in the town of Luvungi and neighbouring villages in North Kivu within miles of a UN base in August.