The man who died in a botched bomb attack in the northern English city of Liverpool on Sunday had planned the blast for at least seven months, police said Wednesday.

Iraq-born Emad Al Swealmeen, 32, rented a property in the city in April and had made "relevant purchases" for his bomb since "at least" that time, said Russ Jackson, who heads counter-terrorism policing in northwest England.

Al Swealmeen's improvised device went off in the back of a taxi outside a Liverpool hospital moments before Britain marked Remembrance Sunday last weekend.

He was killed in the fireball, while the quick-thinking taxi driver escaped with minor injuries after reportedly locking Al Swealmeen inside his cab.

"A complex picture is emerging over the purchases of the component parts of the device, we know that Al Swealmeen rented the property from April this year and we believe relevant purchases have been made at least since that time," said Jackson.

"We have now traced a next of kin for Al Swealmeen who has informed us that he was born in Iraq."

The failed asylum seeker suffered from bouts of mental illness that will "form part of the investigation and will take some time to fully understand" said Jackson.

Al Swealmeen was taken in by Elizabeth and Malcolm Hitchcott, a Christian volunteer couple in Liverpool, for eight months from 2017 as his appeal for refugee status played out.

Elizabeth Hitchcott told the BBC she felt "just so sad" and "very shocked" by Sunday's incident, adding: "We just loved him, he was a lovely guy."

Malcolm Hitchcott told ITV News that Al Swealmeen spent time in a mental institution after being arrested with a knife in an incident in central Liverpool.

Conversion questions

The Times newspaper reported that the improvised device contained TATP -- the same explosive favoured by the Islamic State group that was used in the 2015 Paris attacks and the Manchester Arena bombing in 2017.

The blast was the second terror-inspired attack in Britain in the last month, after a British MP was stabbed to death as he met constituents in southeast England in October.

The two incidents prompted the government on Monday to raise the terror threat level from "substantial" to "severe" -- the second-highest -- meaning an attack was "highly likely".

It has also brought Britain's asylum policy under scrutiny, at a time when London is seeking to tighten its borders, particularly against migrants crossing from France over the Channel.

Home Secretary Priti Patel said Al Swealmeen had been able to exploit Britain's "dysfunctional" immigration system and stay in the country, despite having been rejected for asylum, British media reported.

His conversion to Christianity has also prompted discussion about whether some asylum seekers were using the process to bolster their case to stay in Britain.

Liverpool Cathedral, where Al Swealmeen was baptised in 2015 and confirmed in 2017, said it had "robust processes" in place to determine a person's "genuine commitment".

Malcolm Hitchcott told BBC local radio he was convinced about Al Swealmeen's religious conviction.

"I was in no doubt by the time that he left us at the end of eight months that he was a Christian," he said.