The FBI reportedly warned British intelligence agencies in January that Salman Abedi, who killed 22 people in a suicide bombing in Manchester last week, was planning to carry out a terrorist act.

A security source told The Daily Mail on Sunday that US intelligence had told MI5 that Abedi belonged to a North African Islamic State cell that was plotting an attack in the UK.

In addition, two people who knew Abedi while he studied at Manchester College in 2012-2013 made separate calls to a terrorism hotline to warn officials of his extremist views, the BBC reported.

Abedi, a 22-year-old Briton of Libyan descent, died last Monday when he detonated a bomb as crowds were leaving an Ariana Grande concert.

According to reports, the US placed him on a terror watch list in 2016.

“In early 2017 the FBI told MI5 that Abedi belonged to a North African terror gang based in Manchester, which was looking for a political target in this country,” the Mail quoted a British source as saying.

CCTV image of Salman Abedi in an unknown location on the night of the attack he carried out on Manchester Arena, May 22, 2017. (Greater Manchester Police via AP)

CCTV image of Salman Abedi in an unknown location on the night of the attack he carried out on Manchester Arena, May 22, 2017. (Greater Manchester Police via AP)

According to the source, US intelligence agents had intercepted communications between Abedi and his family in Libya, who were linked to known terrorist groups.

“Following this US tip-off, Abedi and other members of the gang were scrutinized by MI5. It was thought at the time that Abedi was planning to assassinate a political figure,” the source said. “But nothing came of this investigation and, tragically, he slipped down the pecking order of targets.”

The Mirror reported that Abedi was banned from a local mosque after criticizing its imam for condemning the Islamic State terror group.

Britain's Home Secretary Amber Rudd arrives at Downing Street in central London on May 24, 2017, (AFP/Justin TALLIS)

Britain’s Home Secretary Amber Rudd arrives at Downing Street in central London on May 24, 2017, (AFP/Justin TALLIS)

In response to the criticism that authorities failed to prevent the attack, Amber Rudd, the home secretary, said Sunday that intelligence agencies were monitoring 3,000 suspected extremists and had a wider pool of 20,000 people of interest.

“I would not rush to conclusions… that they have somehow missed something,” Rudd said.

In the wake of the terror attack, MI5 has launched two separate investigations into how it failed to intercept Abedi, including an internal MI5 inquiry launched on Monday.

Police have so far arrested 16 people, two of whom were subsequently released. Cops said that 1,000 people are working on the investigation, trying to track down Abedi’s accomplices and piece together his movements in the days before he carried out the attack.

Investigators say they have dismantled a large part of his network, but expect to make more arrests.

“The operation is still at full tilt,” Rudd said, adding that some suspects could remain at large.

“Until the operation is complete, we can’t be entirely sure that it is closed,” she said.

The suspects in custody include Abedi’s elder brother Ismail, as well as their father, Ramadan, and another brother who was detained in Libya.

Agencies contributed to this report.