Which is interesting, because the IDF says that it hit terrorists about to shoot rockets into Israel - and Hamas claims that they don't fire rockets.
The IDF says that three were killed, but as of this writing I cannot find out the affiliation of the third one killed. The Hamas Al Qassam site seems to imply that those badly injured were theirs as well, so chances are that the third was also Hamas.
Interestingly, Palestine Times says that eyewitnesses said that the Hamas members were indeed about to shoot rockets into Israel.
UPDATE: The count is up to four. The third was with the PRC, the affiliation of the fourth is still unclear.