British counter-terrorism police probing the arena suicide bombing in Manchester that killed 22 people on Friday discovered a car in the city which they believe could be "significant" to the investigation.

Greater Manchester Police said that officers have set up a cordon in the Devell Court area of Manchester while they assess the vehicle.

"This is potentially a significant development in the investigation. The car has been located at Devell Court," said Detective Chief Superintendent Russ Jackson.

"We are very interested in anything people can tell us about the movements of this car, and who was in it, over the past months. We are also interested in any information about who may have had access to the car or who may have gone to and from it," he said.

He also reiterated a police appeal for information to piece together the movements of 22-year-old suicide bomber Salman Abedi before he blew himself up at Manchester Arena on May 22, killing 22 people.

The discovery of the car came as two of Abedi's cousins, Isaac and Abz Forjani, said they believe he was acting alone and not as part of any wide terror network.

The duo, who were among those arrested by police in the aftermath of the bombing and since been released without charge, say they did not know about their cousin's extremist views and that he may have been radicalised abroad.

"I believe it was all done by one man, (who) developed some sort of thoughts in the past few years which he kept to himself, secretly to himself. He never shared it with any members of the family – if he would of, we could have done something to stop that happening. He never admitted extremist views There's never been a hint of extremism," said 21-year- old Abz Forjani.

The brothers stressed they were "Mancunians", or local Manchester natives, who held similar British values as others in the city.

"It's not easy being connected to 22 lost, innocent lives. The fact that the person that did this is related to us by blood is something that's going to stay with me for the rest of my life. My thoughts are with the families of the victims," said 24-year-old Isaac.

"I really do feel for them. We went in, we could come out, we can try and move on with our lives. They've lost their loved ones," he said.

The two brothers, of Libyan descent, said they last saw Abedi three months before the attack, when he got his hair trimmed at Abz Forjani's barber shop in Manchester.

Their younger brother, 19-year-old Alharth, remains in custody in connection with the investigation.