A new image has been released by British police, showing suicide bomber Salman Abedi on the day he attacked Manchester Arena.

LONDON, May 30 (Xinhua) -- British police on Monday released a picture of Manchester bomber Salman Abedi that showed him with a blue suitcase on the day of the suicide attack last week.

The Greater Manchester Police are appealing for people who might have seen him carrying the blue suitcase between May 18 and 22.

Police believe Abedi returned to Britain around May 18, just days before the May 22 attack which left 22 people dead and 116 injured. More than 50 of the injured remain under treatment in hospital, with 19 in critical care.

"Today, we are releasing an image of Abedi carrying a distinctive blue suitcase and an image of a replica of the case. We know he visited the Wilmslow Road area of Manchester and was also seen in Manchester city centre with the blue suitcase," Detective Chief Superintendent Russ Jackson of the North West Counter Terrorism Unit said in a statement.

He said the police believe Abedi was in possession of this case in the days before the attack.

"I want to stress that this is a different item than the one he used in the attack. This image was taken from CCTV in the city centre on May 22," said Jackson.

"We have no reason to believe the case and its contents contain anything dangerous, but would ask people to be cautious," he said, calling on the public with information about the whereabouts of the case to call the Anti-Terrorist Hotline.