“The danger is that once trained and inspired by conflict on the battlefield, these young men might then return home and become the cause of further trouble,” he wrote in a paper for the Australian Strategic Policy Institute.
“As has been shown before, radicalised young men do not always need an outside commandment to reach the conclusion that they should carry out action.”
The hardline group is engaged in a military offensive against Somalia’s internationally backed government, although it denied any connection to the alleged plot.
Last month it proclaimed its allegiance to Osama bin Laden in a video documentary, underlining al-Qaeda’s growing ideological influence among Somali Islamists.
Pantucci, a consulting research associate at the UK-based International Institute for Strategic Studies, said Shebaab was reaching out to Somalis as far afield as Sweden and Canada.
“At this stage it would seem unlikely that al-Shabaab (Shebaab) would attack the West,” Pantucci wrote.
“What is clear, however, is that we are likely to see an increase in Westernised Muslims appearing on the battlefield in Somalia,” he added.
“Whether they come home to carry out terrorist attacks, or mobilise the networks which sent them to conduct activity back home remains uncertain.
“It would not be surprising, however, if there was an increase in localised targeting of Western interests.”
He added that bin Laden and Ayman al-Zawahiri, al-Qaeda’s second-in-command, had singled out the “lions of Somalia” for praise.