Tunisian engineer Mohamed Zaouari was shot dead in his car in December 2016 by unknown gunmen, with Hamas accusing Israel of responsibility at the time.
Senior Hamas figure Mohammed Nazzal made the allegations on Thursday in a statement and at a press conference in Beirut.
He said an investigation concluded that a number of agents from Israeli intelligence agency Mossad had operated in Tunisia over several months, including pretending to be foreign journalists in order to get close to Zaouari.
The main two assassins who entered the country before the killing were using Bosnian passports, Nazzal said. Israeli Foreign Ministry spokesman Emmanuel Nahshon declined comment. Israel also had not previously commented on the killing.
Israel has previously faced criticism after its agents reportedly used British, Irish, Australian and other passports to assassinate a Hamas leader in the UAE in 2010.
That led to Britain, Ireland and Australia expelling some Israeli diplomats in protest.
Zaouari, 49, was murdered at the wheel of his car outside his house in Tunisia’s second city Sfax on Dec.15 last year.
The engineer and drone expert had worked for a decade with Hamas the group said at the time.