Ashraf al-Kidra says the strike occurred near the southern Gaza Strip town of Khan Younis early Sunday.
It wasn't immediately clear who the men were. But Israel routinely strikes at groups of militants seeking to fire rockets at nearby Israeli communities.
An Israeli military spokeswoman could only confirm that militants were targeted. She spoke anonymously, citing military policy.
The strike comes after two days of calm on either side of the Gaza-Israel border. Earlier this week in fighting, militants fired some 80 salvos at southern Israel and Israeli aircraft struck Gaza four times.
Five Palestinians, including three militants, were killed in the fighting and two foreign laborers in Israel were critically wounded.