Six Palestinians were killed and 30 injured by Israeli shelling and air strikes after militants fired on an Israeli jeep, wounding four soldiers, medics and witnesses said on Sunday.

The flare-up, which began on Saturday, was one of the most serious clashes in a single day since Israel's devastating 22-day operation in the Gaza Strip over New Year 2009.

In the latest in a spate of attacks and counter-attacks between the army and Palestinians, a militant was killed and two other people wounded in an Israeli air strike near the northern town of Jabaliya just before midnight, medics said.

The dead man was named as Mohammed Shwikani, a 20-year-old militant with the armed wing of Islamic Jihad, the group said.

Overnight, the military launched a series of air raids to the north and east of Gaza City, which left two more people injured, Palestinian witnesses and medical sources said.

Early on Sunday, medics reported finding the body of another Islamic Jihad militant who was killed in another air strike which struck east of Jabaliya, raising the death toll to six within 12 hours of bloodshed.

He was identified as Mohammed Abed, 20.

The army confirmed it had attacked seven different targets overnight, including arms dumps, a weapons-making facility and two rocket-launching sites "in response to recent events."

As the air force pounded Gaza, militants fired 36 rockets over the border, injuring four people in the Israeli town of Sderot which lies several kilometres from the border.

The violence first erupted Saturday evening when militants fired an anti-tank missile at an Israeli jeep near the Karni crossing along the border east of Gaza City.

The army confirmed four soldiers had been wounded in the attack, which was claimed by the armed wing of the left-leaning Popular Front for the Liberation of Palestine (PFLP).

Military sources said two of the soldiers were in serious condition.

In response, Israel fired a barrage of artillery fire and shells, killing three people and wounding 25, five of them seriously, medical officials and witnesses said.

One of the injured died later in hospital.

Ashraf al-Qudra, spokesman for the Hamas-run health ministry said some of the injured were in "serious to critical condition," adding the dead and the wounded appeared to be civilians.

A spokesman for Gaza's Hamas government said the four killed were aged between 15 and 20.

Medics also said five Palestinians were wounded in another bout of Israeli shelling near Khan Yunis in southern Gaza.

-- Threats of revenge --

Late Saturday, Israeli Prime Minister Benjamin Netanyahu held talks with his Defence Minister Ehud Barak and Chief of Staff Lieutenant General Benny Gantz to discuss the situation in the south, the premier said on Twitter.

"The IDF (Israeli Defence Forces) responded severely to the incident and additional responses will be examined in the coming days," Barak was quoted as saying in a statement from his office.

The bloodshed was swiftly condemned by the Hamas government, as well as by militant groups, which vowed revenge.

"The occupation attacked Palestinian civilians east of Gaza City and Khan Yunis. We consider this escalation as very dangerous. It must stop immediately," said Hamas spokesman Fawzi Barhum.

The armed wing of the radical Popular Resistance Committees also released a statement vowing that "the Zionist enemy will pay a high price for this crime against Gaza".

And Islamic Jihad also issued a warning, saying: "Every aggression against the Palestinian people will be followed by a response from the resistance."

In recent days, tensions have been rising between Israeli troops and Gaza militants.

On Thursday, an Israeli soldier was wounded near the border east of Khan Yunis when explosives packed into a tunnel were detonated in an attack claimed by Hamas's armed wing, the Ezzedine al-Qassam Brigades.

Several hours earlier, a 13-year-old Palestinian was shot dead by gunfire from an Israeli helicopter in the same area, medics and witnesses said.

And on Tuesday, three Israeli soldiers were wounded in an another explosion in the same area.

An earlier flare-up in and around Gaza began on October 22 and continued for three days, with eight militants killed in Israeli air strikes, and armed groups firing more than 100 rockets across the border, severely wounding two Thais.

In December 2008, just six weeks shy of general elections, Israel launched a huge operation in Gaza to stamp out Palestinian cross-border rocket fire that cost the lives of 1,400 Palestinians -- half of them civilians -- and 13 Israelis, 10 of them soldiers.