LONDON — Hashem Abedi, a key suspect in the 2017 Manchester Arena bombing that killed 22 people, was arrested Wednesday at a London airport after being extradited from Libya, British police said.

Greater Manchester Police said Hashem, the younger brother of deceased suicide bomber Salman Abedi, has been arrested for murder, attempted murder and conspiracy to cause an explosion likely to endanger life. He was taken to a London police station and is expected to appear in Westminster Magistrates' Court in the coming days.

"This is clearly an important moment in the investigation," said British Prime Minister Theresa May. "I hope it is a welcome step for the loved ones of all the victims."

Salman Abedi, who set off the bomb at the end of an Ariana Grande concert on May 22, 2017, died in the explosion, which also wounded hundreds. British authorities have sought Hashem's extradition for nearly two years, saying he was involved in planning the lethal attack.

Ahmed Bin Salem, a spokesman for the Tripoli-based Special Deterrence Force, said they extradited Hashem Abedi from Libya following a court order. The militia is allied with a U.N.-recognized government in the Libyan capital.

Both Hashem, who was then 18, and the boys' father, Ramadan Abedi, were detained by Libyan forces shortly after the attack. Hashem told investigators that both he and his brother belonged to the Islamic State group and that he knew about the attack, the Special Deterrence Force said at the time. The father was not charged and was later released.

The arrest warrant for Hashem Abedi was issued by a Westminster Magistrates' Court judge and approved by Home Secretary Sajid Javid.

Manchester police notified the victims' families earlier Wednesday that the long-awaited extradition was in process. It was slowed by the complicated political and military situation inside Libya.

Libya slid into chaos following the 2011 uprising that toppled and killed dictator Moammar Gadhafi. The country has since become a haven for rival armed groups.

The Tripoli government is currently seeking Western support as it battles forces loyal to Khalifa Hifter, a veteran Libyan general who launched an offensive against the capital in April. The Special Deterrence Force is one of several militias loosely aligned with the government that are battling Hifter's forces.