The Al-Qaeda-linked fighters, in a message posted on Twitter, said "137 hostages who were being held by the mujahedeen" had died.
They also accused Kenyan troops of using "chemical agents" to end the four-day stand-off.
"In an act of sheer cowardice, beleaguered Kenyan forces deliberately fired projectiles containing chemical agents," one tweet read.
"To cover their crime, the Kenyan government carried out a demolition to the building, burying evidence and all hostages under the rubble."
Police said the death toll was provisional, with the Kenyan Red Cross listing 63 people as still missing.
There was no immediate response from Kenya's government, but the Shebab have in past made repeated outlandish claims, especially on their Twitter site.
The Shebab said they carried out the attack in retaliation for Kenya's two-year battle against the extremists' bases in the country.
In one of the worst attacks in Kenya's history, the militants marched into the four-storey, part Israeli-owned mall at midday Saturday, spraying shoppers with automatic weapons fire and tossing grenades.
Close to 200 were wounded in the four-day siege, which saw running battles between militants and security forces in the complex, Nairobi's largest shopping centre and popular with wealthy Kenyans, diplomats, UN workers and other expatriates.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
