Israel says it has tripled the number of its troops in southern Lebanon in an expanded offensive, despite a United Nations vote backing a ceasefire.
Israeli troops in Lebanon are now thought to number 30,000
The soldiers are moving towards the strategically significant Litani River, the military said.
Hezbollah's leader has said the group will abide by the UN Security Council resolution, which calls for a "full cessation of hostilities".
Israel's Cabinet will discuss the issue on Sunday.
It says it will only halt military action after taking a vote.
Lebanese ministers will discuss the UN plan on Saturday. Prime Minister Fouad Siniora indicated he would back the truce call, saying: "This resolution shows that the whole world stood by Lebanon."
Hezbollah's leader, Sheikh Hassan Nasrallah, said on the group's al-Manar TV channel on Saturday that it would abide by the plan.
But referring to Israel's insistence it has the right to continue military operations in Lebanon in self-defence, Sheikh Nasrallah said: "As long as there is Israeli aggression, it is our right to fight them and defend our land."
Israeli Prime Minister Ehud Olmert is asking his Cabinet to endorse the resolution, describing it as positive and acceptable.
More than 1,000 Lebanese and more than 120 Israelis have been killed in the conflict since Hezbollah militants captured two Israeli soldiers on 12 July in a cross-border raid.
Israel's army chief, Lt Gen Dan Halutz, said Israeli troops would remain in Lebanon until the arrival of the UN peacekeeping force - expected to be 15,000-strong.
Gen Halutz did not give a figure for the new number of Israeli troops currently in Lebanon, but Israeli sources put it at about 30,000.
Israel radio said the troops had been ordered to seize ground as far as the Litani River, up to 30km (18 miles) from the Israeli border.
The Israeli army confirmed it had airlifted hundreds of troops by helicopter into positions in south Lebanon.
Full details of the new offensive are unclear but several sources confirm heavy clashes between Israeli troops and Hezbollah fighters at the village of Ghandouriyeh, 11km inside Lebanon.
Ghandouriyeh is a key strategic point, a hilltop village overlooking Hezbollah positions that are just 2.5km from the Litani.
Israeli jets also raided the city of Sidon - north of the Litani - destroying facilities at a power station. It is only the second time Sidon has been hit in the conflict, which began more than four weeks ago.
An Israeli strike on Sidon reportedly cut off power to the port city
According to Lebanese security sources, up to 15 people were killed in an Israeli air strike on the village of Rshaf in south Lebanon.
Israel has said it has killed more than 40 Hezbollah fighters in the past 24 hours.
Hezbollah has also fired more rockets into northern Israel, but Israeli sources say the number is far fewer than in recent days.
The UN special envoy to the Middle East, Alvaro de Soto, said he expected Israel to wind down its operations in the next couple of days.
No timetable has been agreed for a ceasefire.
UN Security Council resolution 1701 was passed unanimously in New York after an impassioned speech from Secretary General Kofi Annan.
On Saturday, US President George W Bush praised the UN move, adding: "I now urge the international community to turn words into action and make every effort to bring lasting peace to the region."
The new resolution says Hezbollah must end attacks on Israel while Israel must end "offensive military operations" in Lebanese territory.
Other key points of the plan include:
- Some 15,000 peacekeeping troops from the existing UN Interim Force in Lebanon, Unifil, to receive a strengthened mandate to monitor and enforce the ceasefire
- Lebanon's government to deploy troops to the south of the country, previously the domain of Hezbollah fighters
- Israel to withdraw troops currently in southern Lebanon as UN and Lebanese forces are deployed
- The drawing up of plans for the disarmament of Hezbollah and the final settlement of the Israel-Lebanon border area, including the disputed Shebaa farms area.