The bomber who killed 22 people at a pop concert in Manchester, England, last month had met in Libya with members of an Islamic State unit linked to the 2015 Paris terrorist attack, according to current and retired intelligence officials.

The content of the communications between the attacker, Salman Abedi, and the terrorist cell remain unknown. But the possibility that he was directed or enabled by Islamic State operatives in Libya, as opposed to Syria, suggests that even as the group’s Middle East base is shrinking, at least one of its remote franchises is developing ways continue attacks within Europe.

On visits to Tripoli as well as to the coastal Libyan town of Sabratha, Mr. Abedi met with operatives of the Katibat al-Battar al-Libi, a core Islamic State unit that was headquartered in Syria before some of its members dispersed to Libya.