The 33-year-old confessed to having killed at least 42 women since 2022, police say.
Aliko Dangote says he only owns two houses, so he can use his wealth to build his businesses in Nigeria.
The leader of the East African country has won over 90% of the vote in all the elections he has run in.
Human rights groups had urged MPs to block the bill, introduced after pressure from Muslim clerics.
"I saw injured people screaming for help - it was terrifying," one survivor tells the BBC in Mogadishu.