Liverpool bomber started buying bomb parts in April

The perpetrator of Sunday's attack outside a hospital in Liverpool (England) began buying the components of the explosive device in April, said Russ Jackson, head of the counter-terrorism unit in the northwest of England, on Wednesday.

The bomber, identified as Emad al-Swealmeen, was killed when the explosive device detonated inside the taxi he was travelling in, while the driver was injured.

According to law enforcement officials, al-Swealmeen was born in Iraq, rented a property in Liverpool and at least since April began making "relevant purchases" to assemble the homemade bomb, which exploded on Sunday morning outside Liverpool Women's Hospital.

"A complex picture is emerging about purchases of components for the device. We know that Al-Swealmeen had been renting a property since April this year and we believe he was making relevant purchases at least since that time," Jackson said.

The police officer also reported that the 32-year-old man was an asylum seeker with mental health problems.

"This will form part of the (police) investigation, and we will take time to understand everything," he added.

Following the attack, the British government on Monday raised the terror alert level in the UK from "substantial" to "severe", meaning that the possibility of an attack is "highly likely".