Israeli jets have carried out fresh air raids on tunnels under the Gaza-Egypt border, reportedly sending hundreds of people fleeing their homes in panic.
Local residents and Hamas security officials said three air attacks took place before dawn on Wednesday, but no casualties have yet been reported.
The raids came just hours before the newly appointed US Middle East peace envoy was due to arrive in Israel, and after an attack on an Israeli army patrol that killed an officer and wounded three other soldiers.
"IAF [Israeli Air Force] aircraft recently hit a number of Hamas smuggling tunnels on the Southern border of the Gaza Strip," a statement released on Wednesday by the Israeli army said.
"This was in response to the attack against an IDF [Israeli army] force in the area of Kissufim on the morning of January 27th, in which one IDF warrant officer was killed and three other IDF personnel were wounded, including one severe injury, when Palestinians detonated an explosive device against an IDF force patrolling on the Israeli side of the Gaza Strip security fence."
Israel says the attacks on the Rafah tunnels are aimed at stopping alleged weapons smuggling into the Gaza Strip by Hamas fighters.
The tunnels are also used to smuggle food, fuel and consumer goods from Egypt and are considered a life-line for thousands of ordinary Gazans.
The Israeli raids came as George Mitchell, the US envoy to the Middle East, began a tour across the region aimed at promoting a durable peace between Israel and the Palestinians.
He began his tour itinerary in Egypt on Wednesday, holding talks with Hosni Mubarak, the country's president. Mitchell is set to head to Jerusalem later in the day.
The latest attack came despite fragile ceasefires declared by Israel and Hamas last week, ending a 22-day Israeli military campaign on Gaza in which 1,300 people were killed.
Israeli jets had targeted scores of cross-border tunnels during the recent war, but many tunnels resumed work shortly after the ceasefire.
An air raid shortly afterwards killed one Palestinian on a motorcycle whom an Israeli army spokesman identified as the planner of the roadside bomb attack.
Hamas confirmed that one of its members riding a motorcycle was injured in the attack in the town of Khan Younis.
Neither Hamas nor any other group has claimed responsibility for Tuesday's bomb attack targeting an Israeli army patrol along the Gaza border.
Ehud Olmert, the Israeli prime minister, said late on Tuesday that the killing of the man on the motorcycle was only an initial reaction and that Israel's full response was still to come, Israeli media websites reported.
After the incident, Israeli forces opened fire, killing a Palestinian farmer, Palestinian medical workers said.
Speaking on Tuesday's incidents, Dr Moaiya Hassanain of Gaza's health ministry confirmed that a 27-year-old farmer was killed by Israeli gunfire along the border, which also left two other Palestinians wounded.
Israel subsequently closed its border crossings to humanitarian aid traffic late on Tuesday after briefly opening them in the morning.
Raed Fattouh, a Gaza border official, said Israeli officials informed him the closure was due to the attack.
Describing the attack on the Israeli patrol, Al Jazeera's Tamer Mishal reporting from Gaza said that an anti-armour shell was fired from inside the territory at an Israeli tank near the area of Khan Younis.
Residents of Kissufim said the Israeli army patrol and Palestinian fighters exchanged fire shortly after the blast.
Egyptian mediators have been talking separately to Israel and Hamas to negotiate a more permanent ceasefire.
Hamas wants the border crossings into Gaza reopened, including the Rafah checkpoint bordering Egypt, to end the Israeli blockade in the territory.
Israel wants to stop the rocket fire and prevent Hamas fighters from using smuggling tunnels under the border with Egypt to rearm themselves with weapons.