The group says today's explosion took place at a training site in the northern Gaza Strip. It identified the dead man as Mazen Lulu, 30, saying he was killed in a "Jihadi mission," a term typically used to describe work accidents.
Local media reported that two other fighters were also wounded. No other information was provided.
Since the beginning of this year, 14 members of Hamas, the militant Islamic group that rules Gaza, have been killed in tunnel collapses that have also been referred to as work accidents.