"The investigation carried out by the United Nations (news - web sites) Interim Force in Lebanon (UNIFIL) command has shown that the Israeli bulldozer was inside Lebanese territory," Lahoud said in a statement.
"And this constitutes a clear violation of the Blue Line," said Lahoud, referring to the demarcation line marked out by UNIFIL when Israel ended its 22-year occupation of south Lebanon in May 2000.
An Israeli army spokesman had charged earlier that, although the bulldozer was a few metres (yards) north of the border fence at the time of the attack, it was still on Israeli soil as the Blue Line ran along a river 10 metres (yards) north of the fence.
There was no immediate confirmation from UNIFIL of its findings.
Lahoud recalled that "Israel had assassinated two Lebanese civilians just because they were suspected of being close to the Blue Line" on December 9.
Lebanese authorities then said the two slain men were hunters killed on the Lebanese side of the border and had lodged an official complaint with the United Nations.
Lahoud warned that "the daily Israeli provocations on the southern border, through air and ground violations, put Israel in a position where it bears the responsibility of the consequences."
He accused Israel of ignoring "urgent calls made by the representative of the UN secretary general in southern Lebanon (Staffan de Mistura) ... for a halt to these violations, most recently in a statement yesterday (Monday)."
Monday's flare-up followed a sharp escalation of Israeli aerial activity in the skies over Lebanon which drew artillery fire from Hezbollah and a stern rebuff from UN peacekeepers.
"The UN reiterates its call upon the Israeli authorities to cease its continuing air violations of the line of withdrawal and Lebanese airspace," de Mistura said.