At least four Israeli soldiers have been wounded after two armed men breached the buffer zone between the Gaza Strip and and opened fire

Al Jazeera's Stefanie Dekker, reporting from Gaza City, said there was no confirmation of how seriously the four Israeli soldiers in Kibbutz Nirim, east of Khan Younis, were injured or who carried out the attack.

"But certainly, it's not very common that the buffer zone is breached," Dekker said. "It is a very tightly, security-controlled area, so we're surprised that the militants have been able to cross it."

She reported that after the incident, more Israeli soldiers appeared at the scene and opened fire, but what happened to the armed men remains unclear at the moment.

The buffer zone is made up of 300 metres of Palestinian land - within the Gaza border - which Palestinians are not supposed to enter, even though the area contain farmland.

An exchange of fire

Israeli television's channel 10 reported that Israel troops opened fire after spotting a group of Palestinians apparently trying to place a bomb near the security barrier that separates Gaza from Israel and close to the Beeri kibbutz in Israel.

It said the Palestinians returned fire.

Witnesses told AFP that the firefight lasted 20 minutes, and that one Palestinian was said to have been wounded.

Earlier on Friday, a projectile fired from the Gaza Strip fell on southern Israel, Israeli military sources said.

Israel's military usually replies to such attacks with air raids on Gaza, which is controlled by Hamas.

Late on Thursday, warplanes bombed three sites across Gaza, causing no casualties, Palestinian security officials and witnesses said. The Israeli military confirmed attacking only two targets.

On Wednesday, Palestinian fighters fired seven projectiles, most of them mortar shells, without causing any casualties or damage, the army said.

And that night, Israeli troops shot dead two Palestinians who they said were trying to get across the border fence into Israel.

Source: Al Jazeera and agencies