Hashem Abedi, the younger brother of the Manchester suicide bomber Salman Abedi, has been arrested in Libya and admitted they were members of the Islamic State extremist group, Libyan authorities said Wednesday.

Hashem, a 20-year-old university student in Manchester, said he had known Salman's attack plan beforehand and was planning a terror attack himself in Tripoli after leaving Britain on April 16, according to the security authorities.


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Hashem had received some 4,500 dinars ($3,250) from Salman, they said, adding the authorities had been following Hashem for about 90 days.

Reuters reported that the father of the two has also been arrested, although it was not immediately known on what charges.

Salman, 22, who was born in Manchester from a family of Libyan origin, has been named as the culprit in the suicide bombing of a concert venue packed with children in Manchester, northern England, which killed 22 and injured 59 others.

The Islamic State militant group has claimed responsibility for the blast at the concert of U.S. pop singer Ariana Grande.

The Wall Street Journal reported Salman's younger sister in Libya as saying that she thinks Salman was motivated by revenge because "he saw children -- Muslim children -- dying everywhere."

British police have arrested seven people in connection with the attack so far, as they try to close down a terror network behind the bomber.

The Daily Telegraph reported that in the five years prior to Monday night's deadly attack, Salman's friends had warned authorities of the danger he posed on at least five separate occasions.

Meanwhile, members of the armed forces have been deployed to patrol locations in London and other parts of the United Kingdom, after the country's terror threat level was raised from "severe" to "critical," suggesting that further attacks are likely.