Kenya's Westgate siege: Security chiefs to be quizzed 30 September 2013 Last updated at 00:42 Top Kenyan security officials are to be questioned by MPs about alleged intelligence failings over the deadly Westgate shopping centre attack. The head of the parliament's defence committee says "people need to know the exact lapses in the security system." There are reports the NIS intelligence agency issued warnings a year ago. Some 67 people were killed and many injured after al-Shabab militants stormed the Westgate centre in the capital Nairobi on 21 September. Five militants were killed by the security forces during the four-day siege and 10 people have since been arrested, the authorities say. Al-Shabab, a Somali Islamist group, said the attack was in retaliation for Kenya's military involvement in Somalia. Operation's 'anatomy' Security officials - including the head of the National Intelligence Service (NIS), Michael Gichangi - are set to appear before the parliamentary defence committee later on Monday. Committee head Ndung'u Gethenji has told the BBC that "people need to know the exact lapses in the security system that possibly allowed this event to take place." Kenyan newspapers have reported that the NIS warned a year ago of the presence of suspected al-Shabab militants in the capital and that they were planning suicide attacks, including on the Westgate shopping centre. A dossier from the NIS - amounting to more than 8,000 pages according to Kenya's Standard newspaper - also suggests the Israelis issued warnings that buildings owned by its citizens could be attacked between 4 and 28 September. The Daily Nation has reported that Kenyan intelligence had established that al-Shabab leaders had begun singling out Westgate and the Holy Family Basilica for attack early this year. Government figures said to have received the intelligence briefings include Interior Minister Joseph Ole Lenku, Treasury Minister Julius Rotich, Foreign Affairs Minister Amina Mohammed, Defence Minister Raychelle Omamo and Kenya Defence Forces chief Julius Karangi. On Sunday, Mr Lenku refused to answer questions on the issue, saying the information was confidential and would not be discussed in public. However, a senior interior ministry official earlier denied that ministers had ignored intelligence warnings. The official - who was speaking on the condition of anonymity - told the BBC the government received intelligence daily, that action was taken and that many attacks had been averted.