Brigadier-General Shuki Shahur, a senior Israeli commander, said Israel would resume full air strikes after the partial suspension which Israel said was to give civilians time to leave.
The army said on Tuesday that it had warned residents north of Lebanon's Litani river to leave the area, suggesting air raids could target areas further north than most previous strikes.
"There are a small number of places north of the Litani river where we know Hezbollah operates, where leaflets were distributed," an army spokeswoman said.
The army had earlier denied distributing any leaflets.
Israel's security cabinet early on Tuesday approved a military ground sweep of 6-7 km into southern Lebanon but not the taking of all territory up to the Litani, political sources said.
The river, 20km from the Israeli border, is seen as a strategic boundary.
Israel's preparation for a fresh push into Lebanon comes as European Union foreign ministers called for an immediate end to hostilities, watering down demands for an immediate ceasefire at the insistence of Britain and other US allies.
An Israeli warplane flies over the
port city of Tyre on Tuesday
The United Nations has postponed discussion on mobilising an international force for Lebanon until at least Thursday, to wait for more progress towards a political solution.
Also on Tuesday, the United Nations scraped two aid convoys planned for villages close to Lebanon's southern border because it could not get security clearance from Israel or Hezbollah.
Israeli forces thrust into southern Lebanon on Tuesday and pounded towns and villages, meeting fierce resistance from Hezbollah fighters who reportedly killed three soldiers.
Despite what Israel had said would be a 48-hour partial halt to air raids, Israeli aircraft bombed eastern Lebanon near Syria on Tuesday, Lebanese security sources and witnesses said.
The raids were aimed at "preventing the transferring of weaponry" to Hezbollah, the Israeli army said.
Israel had said it would use air strikes against Hezbollah and to back ground forces.
Elsewhere, Israeli artillery shells crashed down on the border area around the Lebanese village of Aita al-Shaab, where Hezbollah said it had destroyed a tank in battles with Israeli troops and inflicted 35 casualties in house-to-house battles.
Aita al-Shaab after Israeli air
raids on Tuesday
Three Israeli soldiers were reported killed.
Aljazeera's correspondent reported heavy artillery on Kafir Shoba and air raids on al-Khiyam town in southern Lebanon.
Israel's justice minister said about 300 of an estimated 2,000 Hezbollah fighters have been killed in three weeks of fighting, and the tourism minister later said 400 had been killed.
Hezbollah, which says it does not hide its dead, has announced 43 deaths.
Shahur said thousands of Israeli troops were fighting Hezbollah fighters on several fronts inside south Lebanon.
"We have so far now about six efforts running inside Lebanon ... brigade size or even bigger than brigade size efforts in each one of them," Shahur said in northern Israel.
A brigade is usually made up of more than 1,500 troops.
Shahur said Israel controlled most of Lebanon's Litani river, and that some parts of the river could be controlled without ground forces, but from the air and by long-range artillery.
At least 617 people, mostly civilians, have been killed in Lebanon. The health minister put the toll at 750, including bodies buried under rubble. Fifty-one Israelis have been killed.