Israel has launched an operation in Lebanon to root out the Tehran-backed armed group Hezbollah, which drew Lebanon into the wider Middle East war by launching missiles on behalf of its sponsor.

A ceasefire meant to have gone into force in April was never observed, and a new conditional truce announced after Lebanese-Israeli talks in Washington this week was flatly rejected by Hezbollah hours later.

Lebanon has vowed that it will disarm Hezbollah over time, but has also denounced Israel's invasion, accusing it of employing scorched earth tactics to drive civilians out of southern towns and villages.

In the latest incident, the Lebanese army said, two officers and a soldier were killed in a strike on a military vehicle on the road between Khardali and Nabatieh.

The Israeli military said the vehicle targeted was "moving suspiciously" in "an active combat zone" in an area it had ordered evacuated ahead of operations.

But it insisted that it "operates against the Hezbollah terrorist organisation, not against the Lebanese army", and added it was "reviewing the incident".

Hezbollah dubbed the attack a "heinous crime" and accused the Lebanese government of exposing its own country to bloodshed through its "complete surrender to the enemy's demands in Washington".

The truce deal announced this week would require Hezbollah to stop firing and withdraw from near the Israeli border, and would see Lebanon's army deploy to new "pilot zones" in the area where it will exercise exclusive control.

But Hezbollah's chief rejected the agreement, demanding a full Israeli withdrawal.

- 'Flagrant violation' -

The Lebanese army said Saturday that "the continuation of the deliberate and repeated brutal Israeli aggression... is aimed at thwarting all efforts to reach a solution".

Lebanese President Joseph Aoun also denounced the attack, calling it a "flagrant violation of Lebanese sovereignty... despite Lebanon's efforts in the Washington negotiations to put an end to the continued Israeli aggression that goes unchecked".

Prime Minister Nawaf Salam called it "a heinous crime and an attack on Lebanon and all Lebanese people".

Both Aoun and Salam on Friday had accused Iran of using Lebanon as a "bargaining chip" in talks to end the wider war, with Aoun telling Tehran to stop interfering in his country.

Iran insists Lebanon be included in any agreement with the United States to end the Middle East conflict.

Lebanese army chief Rodolphe Haykal left for Pakistan on Saturday, in a visit linked to Islamabad's mediation efforts between Iran and the US, a source with knowledge of the matter told AFP.

In a statement, the army said Haykal was travelling "at the invitation of his Pakistani counterpart, Field Marshal Syed Asim Munir".

Pakistan hosted an initial round of talks between the US and Iran, and Munir has been involved in mediation efforts since.

"Lebanon is a critical part of the negotiations," the source added, requesting anonymity.

- Trading attacks -

On Saturday, Israel renewed evacuation orders for five villages in Lebanon's south and east, telling residents to move north of the Zahrani River.

Its military later said that it had struck around 150 Hezbollah targets in southern Lebanon over the past two days.

The Israeli army conducted several strikes across south and east Lebanon, according to Lebanese state media.

The Hiram hospital in southern Lebanon's Tyre said one of its nurses was killed in a strike while heading to work.

Hezbollah meanwhile said it had targeted Israeli troops in southern Lebanon, and an artillery position near Israel's side of the border.

Israel's extensive campaign of airstrikes and a ground invasion have killed nearly 3,600 people, according to Lebanon's health ministry.