Hamas sources and medical workers told the Reuters news agency that Israeli ground troops had crossed into Gaza during the incident, prompting and exchange of gunfire.
The Israeli military denied that there had been any shooting on Saturday.
It was not immeditaely clear if the two incidents were related.
On Tuesday, Israeli forces killed at least six Hamas fighters in a series of air raids and a ground attack that was the first lethal confrontation since the two sides agreed a ceasefire in June.
Since then more than 50 rockets have been fired into Israel from Gaza.