Five Israeli aircrew were missing and presumed dead after the helicopter was reportedly shot down by a new type of missile on Saturday night in the Lebanese town of Yater 6 km (4 miles) north of the border.
The Israeli army said it was the first aircraft shot down in Lebanon since fighting with Hezbollah erupted on July 12.
In Beirut, a Hezbollah spokesman said the Shia group had shot down the aircraft in the border village of Yater.
"The fighters of the Islamic Resistance [the armed wing of Hezbollah] fired rockets at a helicopter carrying troops who were trying to land on the Yater hill," he said.
"It was struck and it fell," he added.
Hezbollah says that the helicopter was shot down by a new type of missile called the 'Waad'.
Across the conflict zone at least 19 Israeli soldiers were killed on Saturday as Israeli forces pushed deeper into Lebanon in an apparent attempt to destroy Hezbollah forces south of the Litani river, 30 km north of the border, before a ceasefire begins on Monday morning.
The Israeli army said that more than 100 soldiers have now died since the start of the fighting in southern Lebanon.
They added that more than 40 Hezbollah fighters had also been killed in the last 24 hours and several rocket launchers destroyed. Hezbollah denied that it had lost that many fighters in the clashes.
Fierce clashes between Hezbollah militants and Israeli troops continued through the night southeast of the port city of Tyre in the region near the border with Israel, Lebanese police said.
The area around the border town of Khiam came under intense artillery bombardment from Israeli forces to protect advancing tanks, they added.
Israeli airstrikes also continued, dozens of raids were carried out in the eastern Nabatiye region, a three-story building and two structures used by Hezbollah's rescue service were destroyed.
Homes were also destroyed in the villages of Kfar, Tebnit and Ansar.
Warplanes also launched five attacks near the eastern town of Baalbeck, destroying three trucks, said police.
Two bridges in the northern Akkar plains that link Tripoli with the Syrian border, were also hit.
Eight other bridges in the area have already been destroyed.