Renewed fighting near the Gaza border on Tuesday threatened a fragile week-long ceasefire, as Palestinian militants bombed an Israeli army patrol, killing one soldier, and an Israeli air strike wounded a Hamas militant.

The army patrol was hit near the border town of Kissufim, a move that sent troops across the border into the Gaza Strip in search of the militants.

Heavy gunfire could be heard and Palestinian witnesses said Israeli helicopter gunships unleashed a salvo of machine gun fire into the area, The Associated Press reported.

Besides giving the rough location of the attack, Israel provided few details about the bombing.

There was no immediate claim of responsibility for the bombing, which threatened to fan the embers of three weeks of fighting that has left much of Gaza in tatters and killed close to 1,300 Palestinians.

Israel first launched its offensive in an attempt to put an end to the Hamas rocket fire from Gaza into towns in southern Israel. The offensive was called off on Jan. 17 when both sides agreed, unilaterally, to a truce.

There has been no formal ceasefire agreement between Hamas and Israel, and the Israeli government has vowed to retaliate against any violations of the truce.

In the immediate aftermath of the ceasefire, Israel continued shelling from its gunboats and there were some skirmishes along the border. However, there have been no serious attacks until Tuesday.

After the bombing, Israeli Defence Minister Ehud Barak called an emergency meeting of the country's top military officers.

"We will respond, but there is no point in elaborating," Barak said not long before the air strike, which hit a Hamas militant as he rode a motorcycle in the southern Gaza town of Khan Younis.

Israeli tanks and bulldozers moved into the region after the strike, according to local residents.

In a separate incident, a 27-year-old Gaza farmer was killed by Israeli gunfire several kilometres from the bombing site, according to a representative with Gaza's Health Ministry. Two other Palestinians were also wounded.

The Israeli military did not immediately offer comment on the incident and it is unclear if it is related to the earlier bombing.

After Tuesday's attacks, a Hamas leader, Mushir al-Masri, blamed the Israelis for breaking the truce.

"The Zionists are responsible for any aggression," he said.

He also said Hamas had only agreed to a "lull" in the fighting.

Israel's border crossings into Gaza were closed to humanitarian aid following the Tuesday attack, AP reported.

The violence precedes a visit to the region by Barack Obama's new Middle East envoy, George Mitchell. Mitchell is expected to arrive in the region on Wednesday.

Meanwhile, Egypt, widely seen as a moderate voice in the region, is working to negotiate a longer-term peace agreement.

In addition to demands for an end to rocket fire, the Israelis have demanded international guarantees that Hamas will be prevented from smuggling weapons into Gaza.

Until those two conditions are met, Israel refuses to sign a formal peace deal.

Meanwhile, Hamas is demanding that borders with Egypt and Israel be reopened.