Israeli armoured columns have pushed into Lebanese territory, as troops continue operations against Hezbollah.
Israeli ground troops have been in action close to the border
An Israeli army spokesman said the aim of the overnight raid was to quell rocket fire from the town of Khiam, about 7km (four miles) from the border.
The move did not mark the start of a deeper push approved by the government earlier on Wednesday, he added.
The security cabinet authorised a push towards the Litani River - which lies up to 30km (18 miles) into Lebanon.
Israel says the objective of the planned wider offensive is to destroy Hezbollah positions in the region and prevent the group from firing rockets into Israel.
The Israeli army also said on Wednesday that 15 of its soldiers had died in clashes in Lebanese border villages on Wednesday, the highest number in a single day since the conflict began.
It added that 40 Hezbollah fighters had been killed in the fighting.
Hezbollah fired more than 100 rockets into Israel during the day, but no casualties were reported.
Lebanese Interior Minister Ahmed Fatfat told the BBC he did not understand why Israel was continuing its offensive when Lebanon's government - with the agreement of Hezbollah - had offered to deploy troops in the south.
"We have a real proposal, two days ago, to send the Lebanese army there to make a real peace zone," he said.
"So we didn't understand their reply. They really want war."
But Israeli spokesman Mark Regev said that without "concrete action" from continuing UN negotiations, Israeli could not "sit by idly" as its cities were bombarded by Hezbollah rockets.
At the UN, diplomats are attempting to reword a draft resolution calling for a ceasefire, to take in Lebanese and Arab League demands for an immediate Israeli withdrawal.
Many homes in Hezbollah strongholds have been flattened
On Wednesday differences surfaced again between France and the US - which co-sponsored the original draft - leading some diplomats to express concerns that diplomacy could collapse.
But the BBC's Bridget Kendall at UN headquarters says that there is now a mood of cautious optimism.
The five permanent members of the Security Council held a late-night meeting focusing on the main sticking points - how to get agreement on a ceasefire and Israeli troops out of southern Lebanon, without allowing Hezbollah to rebuild their positions.
Correspondents say the members states are considering a French proposal to deploy Lebanese forces alongside the existing UN force, which would be strengthened, as the Israelis begin a phased withdrawal.
The US has yet to respond - so far it has insisted that any Israeli withdrawal can only follow the deployment of a new, robust multi-national force.
The new proposal is being discussed in members states' capitals before talks resume on Thursday.
Hezbollah's leader, Sheikh Hassan Nasrallah, on Wednesday commented publicly for the first time on the original draft, describing it as "unfair and unjust".
Correspondents say there is still a possibility that the vote - first mooted for early this week - could take place this week, although it may be delayed further.
More than 1,000 people, most of them civilians, have been killed in the month-old conflict, the Lebanese government has said.
More than 100 Israelis, most of them soldiers, have also died.
Israel invaded Lebanon after two of its soldiers were captured by Hezbollah in a cross-border raid on 12 July.