Manchester security service blunders will be investigated

Armed response police stand at the start of the Great Manchester Run in central Manchester. Photo / AP

Missed chances to catch Manchester bomber Salman Abedi will be investigated, the Home Secretary said, as it was claimed that US officials warned MI5 that he was planning an attack.

As the security services faced growing questions over the failure to prevent Abedi from killing 22 people in the Manchester Arena, Amber Rudd said that whether there were "signals" that were not picked up on would be examined.

Despite the terror threat being reduced from critical to severe, she confirmed that members of Abedi's terror network could still be at large.

She spoke after claims that the FBI had told MI5 earlier this year that Abedi was part of a north African terror cell based in Manchester looking to launch an attack.

Yesterday the son of Abdelbaset al-Megrahi, the Lockerbie bomber, warned that the UK faced an unprecedented wave of terror from Libya after it had been abandoned by Western powers and fallen into the hands of terror groups.

Khaled al-Megrahi, whose father was the only man ever convicted of the 1988 bombing, said from his home in Tripoli: "It is only a sea between us. A lot of Libyans are hungry, have no money and no justice. If the West continues its stance, you will see a lot of the militants coming to the UK".

US federal agents had been monitoring Abedi since last year and had passed on information from Libya and from intercepting his communications, it was said.

"Following this US tip-off, Abedi and other members of the gang were scrutinised by MI5. It was thought at the time that Abedi was planning to assassinate a political figure.

"But nothing came of this investigation and, tragically, he slipped down the pecking order of targets," a source told the Mail on Sunday.

Abedi was also reported to authorities by residents at least five times in five years.

Rudd said: "Of course people will want to look afterwards to see whether there are signals that could have been learnt, how could we do this better."

"Signals" are normally used by the intelligence services to refer to emails

She added: "There is - the operation is still at, really at full tilt in a way and so until the operation is complete we can't be entirely sure that it's closed."