Swedish authorities say the failed bombing in Stockholm appeared to be "well-planned" and they suspect more than one person was involved in the botched attack.

Taimour Abdulwahab al-Abdaly killed himself and wounded two people when he targetted the Swedish capital on Saturday afternoon.

Police are now minutely examining material left by the 28-year-old for clues about his accomplices.

An audio message emailed to police and Swedish news agency before the attack is being listened to. There is speculation among counter-terrorism experts that a cough on the recording may be from another person.

Jihadist websites were filled with tributes to the bomber, including poems and epitaphs describing him as a "hero martyr".

Swedish officials said on Monday Abdulwahab apparently carried out his mission alone but had backing from others.

Chief public prosecutor Tomas Lindstrand said: "We know from previous experience that this type of crime usually involves more than one individual.

"The attack appears to have been well-planned, and we assume that the suicide bomber had accomplices."

Officers have also cordoned off Abdaly's family home in Luton where he was living with his wife and three children.

Swedish investigators said he visited his family in Tranas, where his father was celebrating his birthday.

But on Saturday he loaded his white Audi with gas canisters and travelled to Stockholm to wreak carnage on streets packed with Christmas shoppers.

Evidence from the scene indicated that the car failed to explode and al-Abdaly was killed about 300 yards away when explosives strapped to his chest detonated.