Manchester bomber Salman Abedi apparently wasn't the only member of his family to harbor extremist views, as Libyan officials arrested the suicide bomber's father and two brothers and uncovered what investigators called a plot for a new attack.

Hashim Abedi, who was born in 1997, was arrested in Tripoli on Wednesday evening by the Libyan counter-terrorism force Rada on suspicion of links to the Islamic State, and was planning a new attack on the Libyan capital, a government spokesman told Reuters on Wednesday.

The father of the bomber was arrested in Tripoli on Wednesday, a Libyan security spokesman told The Associated Press. The father, Ramadan Abedi, had said another brother of the bomber, Ismail, was arrested Tuesday.

What's more, two U.S. defense officials confirmed to Fox News that Salman Abedi spent three weeks in Libya prior to the Manchester bombing, returning to England just days before the Ariana Grande concert Monday, when he launched his attack at the concert venue.

Salman's mother, Samia Tabbal, is believed to have returned to Libya, while the Facebook profile for his sister, Jomana, suggests that she still lives in Manchester. The mother was described in an article by The Guardian as a “very nice woman” who taught a friend's daughter to read the Quran.

Earlier, Abdel-Basit Haroun, a former security official in Libya, told The Associated Press that he personally knew Ramadan Abedi and that the elder Abedi was a member of the Libyan Islamic Fighting Group in the 1990s. The group had links to Al Qaeda.

Although the LIFG disbanded, Haroun said the father belongs to the Salafi Jihadi movement, the most extreme sect of Salafism and from which Al Qaeda and the Islamic State group hail. Haroun added that Abedi, also known as Abu Ismail, had returned to the Libyan capital of Tripoli.

The LIFG was founded in 1995, and was involved in attempts to assassinate then-Libyan leader Moammar Qaddafi as well as violent clashes with Benghazi police. In 2002, a senior LIFG commander, Anas al-Libi, who also was a companion of Al Qaeda founder Usama bin Laden, was detained by U.S. forces for his role in the 1998 bombings of the American Embassies in Kenya and Tanzania, which killed more than 200 people.

The group also was involved in the bloody riots at Abu Salim prison near Benghazi in 1996 that killed more than 1,200 prisoners.

The LIFG reportedly teamed up with the Moroccan Islamic Combatant Group in planning the May 2003 bombings in Casablanca, Morocco, that killed more than 40 people and injured more than 100. The group also has been linked to the 2004 attacks in Madrid that killed 194 people.

We don't believe in killing innocents. This is not us. — Ramadan Abedi, the father of Manchester bombing suspect Salman Abedi

Ramadan Abedi escaped Tripoli in 1993 after Qaddafi’s security authorities issued an arrest warrant and eventually sought political asylum in Britain. The elder Abedi first immigrated to London before settling in the Whalley Range area of south Manchester, where they had lived for at least a decade.

The neighborhood is known to be home to a number of former LIFG members living in exile, including Abd al-Baset Azzouz – an expert bomb-maker who left Manchester to run a terrorist network in eastern Libya overseen by Ayman al-Zawahiri, Usama bin Laden’s successor as leader of Al Qaeda. Media in the United Kingdom reported in 2014 that Azzouz had 200 to 300 militants under his control.

In a telephone interview from Tripoli, Ramadan Abedi -- who is now the administrative manager of the Central Security force in the Libyan capital -- denied to The Associated Press that his son is linked to any militant group or the suicide bombing that killed 22 people.

The father of the alleged terrorist said that his family "aren't the ones who blow up ourselves among innocents."

"We don't believe in killing innocents. This is not us,” he said.

Abedi added that he spoke to his son five days ago and he was getting ready to travel from Saudi Arabia to Libya to spend the holy month of Ramadan with family and sounded "normal." He said that his son visited Libya a month-and-a-half ago.

The Abedi family had apparently become concerned about Salman’s growing radicalization and a friend close to the family told The New York Times that his parents had seized the suspected bomber’s British passport. They had returned it when he said that he wanted to travel to the holy Saudi city of Mecca, but instead flew back to the Manchester area.

While early reports were unclear whether the 22-year-old Abedi had acted as a lone wolf or in coordination with others, Manchester's police chief told reporters on Wednesday that it is clear "this is a network we are investigating" as he gave an update on the probe into the bomb attack.

Chief Constable Ian Hopkins said Wednesday that police are carrying out extensive searches across Manchester as part of their probe.

Hopkins declined to comment on whether police have found the alleged maker of the explosive device used in Monday night's attack.

His comments followed media reports that Abedi acted as a "mule" for others.

Fox News' Lucas Tomlinson and The Associated Press contributed to this report.