Speaking Monday night in London with British counterpart Jack Straw after talks on the killing of a Brazilian by anti-terror police, Amorim said Brazil "understands the plight" faced by Britain following two sets of bomb attacks on London in a fortnight.
However he stressed that "combating terrorism has to be done with full respect of human rights."
"If things did happen the way it happened in this case, it could play into the hands of the terrorists," Amorim said.
Jean Charles de Menezes, a 27-year-old Brazilian electrician, was shot eight times Friday after running from plain clothes police who suspected he was a suicide bomber. Security sources claimed Monday he had fled because his visa had expired; however Straw said he understood de Menezes was in the country legally.
Hundreds of protesters marched through de Menezes' home town of Gonzaga in the state of Minas Gerais demanding arrests be made.
The case is being investigated by the Independent Police Complaints Commission.