Following the explosion, tanks stormed into Gaza near the town of Deir Al-Balah, with an exchange of gunfire erupting between the soldiers and Palestinian fighters, witnesses said.
Israeli military jets were also reported to have fired on the area indiscriminately.
One Palestinian was killed and another wounded in an Israeli air raid in the northern town of Jabaliya several hours later, Palestinian medical workers said.
Israeli forces had withdrawn from northern Gaza on Monday after a series of deadly raids targeting Palestinian rocket crews left more than 125 people dead - half of them civilians, according to medical officials.
Fighting has persisted sporadically since.
The incident occurred just a day after Condoleezza Rice, the US secretary of state, wrapped up her latest trip to the region saying she had secured a pledge from Israel and the Palestinians to resume peace talks.
Relations with Israel were suspended by Mahmoud Abbas, the Palestinian president, to protest against the Israeli raids.
Abbas has called for a ceasefire between Israel and Hamas but at a news conference with her Israeli counterpart Tzipi Livni on Wednesday, Rice said that a truce was not a condition for the resumption of talks.
She said: ""I have been informed by the parties that they intend to the resume the negotiations and that they are in contact with one another as to how to bring this about."
According to the Palestinian news agency Wafa, Abbas and Rice agreed that a truce - to be mediated by Egyptian officials - should be reached as soon as possible.
The understanding also reportedly included a commitment by Abbas that he would take part in a trilateral US-Israeli-Palestinian meeting to implement the first phase of the so-called road map to peace.
Hamas officials told Al Jazeera that they were open to Abbas's initiative, provided "he has to talk to us first".
Rice also urged Hamas to halt the frequent rocket attacks from the Palestinian territory.
Israel says it would stop land and air raids on Gaza if Palestinian cross-border rocket attacks were halted.
Ehud Olmert, the Israeli prime minister, on Wednesday said: "One thing should be clear: If there is no Qassam [rocket] fire on Israel, there will be no Israeli attack on Gaza.
"We do not rise in the morning and think about how to attack Gaza."