At least four people have been wounded, two of them critically in an Israeli air raid in the Gaza Strip, Palestinian medics say.

The attack took place in a field close to the border a security fence along the border with Israel near the town of Khan Yunis on Saturday, the sources said. 

They said that the wounded men were farmers.

The reports came as the Israeli military said it had detonated two explosive devices it had found.

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.