President Uhuru Kenyatta has vowed not to bow to the Shebab group that claimed the Westgate mall bloodbath and threatened more attacks if Kenya failed to pull its troops out of Somalia.
But his administration faced tough questions after the leaking of an intelligence report dated September 13 which warned of an elevated risk and some top officials said was treated too casually.
Senior security officials told AFP on condition of anonymity that an intelligence report warning of an attack had been sent to the treasury, interior, foreign affairs and defence ministers, as well as the army chief.
The report also said Israel, which has close security ties with Kenya, had warned of plans to attack Israeli-owned property in September, a month which included several Jewish holidays.
The Westgate mall, popular with expatriates and wealthy Kenyans, is part owned by Israelis and had long been considered a prime potential target.
The head of the NIS intelligence agency that produced the report and other top brass are to be grilled by lawmakers on Monday.
"There is no way one can say there was no intelligence on this attack because those reports started trickling in from late last year. And they were specific with targets including Westgate," he said.
"Whenever these reports come, they are shared all across the government with relevant authorities at high levels but they still take them casually."
The media have been awash with reports of the possible involvement in the brazen September 21 commando operation of Samantha Lewthwaite, a white British woman with ties to jihadist groups.