About 60 people were killed in and around Johannesburg on 28 March when supporters of the Zulu Chief Mangosuthu Buthelezi's Inkatha Freedom Party demonstrated against pending all-race elections.
"I gave instructions to our security that if they attack the house, please, you must protect that house even if you have to kill people," Mr Mandela, who held no public office at the time, told the Senate.
Eight people died outside Shell House, the headquarters of Mr Mandela's African National Congress, in the protest and scores more died in townships around the city.
Inkatha accused Mr Mandela of "duplicity" and demanded an inquiry into his role. The party said Mr Mandela prevented a police investigation of the shooting at the time. On Wednesday, 101 survivors and relatives of victims of the shooting filed a lawsuit against Mr Mandela and the ANC for damages of 10 million rand (pounds 1.75m).Reuse content