LONDON, Nov 1- British police said on Wednesday they had issued an arrest warrant for the brother of a suicide bomber who killed 22 people in an attack on a pop concert in Manchester in May and prosecutors had asked Libya to extradite him.Salman Abedi, a 22-year-old Briton born to Libyan parents, blew himself up at the end of a show by US singer Ariana Grande in the deadliest militant attack in Britain for 12 years. His victims included seven children, and more than 500 were injured.Assistant Chief Constable Russ Jackson, who is responsible for counter-terrorism in northwest England, said police had now applied for and been granted an arrest warrant for Abedi's younger brother Hashem for murder, attempted murder and conspiracy to cause an explosion."Hashem Abedi is currently detained in Libya and the CPS (Crown Prosecution Service) has now requested that Libyan authorities consider his extradition back to the United Kingdom," Jackson said. "We are grateful for the Libyan authorities considering this request."He added that detectives had not found any evidence of the involvement of any wider network.Islamic State said it was responsible in the immediate aftermath of the bombing but security services have always treated the claim with scepticism.