Palestinian militants in the Gaza Strip wounded four Israeli soldiers with gunshots and mortar fire yesterday as tensions remained high along the border, Israeli television reported.

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. Two soldiers were taken to hospital by helicopter in serious condition and two others treated on the scene, the report said.

The Israeli military confirmed that four soldiers had been wounded but refused to give further details.

Witnesses inside Gaza said the clash between troops and Palestinian militants took place east of the town of Khan Yunis in the Palestinian enclave.

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

Witnesses also reported that the Israeli forces fired tank shells and a rocket during the incident.

Channel 10 also reported that, following the firefight, significant Israeli reinforcements, including tanks, and backed up by air cover, were deployed along the border.

This was the most serious incident for the army in the Gaza area since two soldiers were killed in March 2010.

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

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

Late on Thursday, warplanes bombed three sites across Gaza, causing no casualties, Palestinian security officials and witnesses said.

The air raids hit targets in the southern city of Rafah, in the northern town of Jabaliya and also struck a site which had been previously been used for launching rockets in the Zeitun district, just east of Gaza City, they said.

The Israeli military confirmed attacking only two targets.

“One was a terror site in northern Gaza, the other a terrorist tunnel in the south,” a spokesman said.

Tunnels from Egypt into neighbouring Gaza, used by militant groups and smugglers, are frequent targets of Israeli air raids.

On Wednesday, Palestinian militants 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.