Michel Aoun was vacating Lebanon's presidential palace on Sunday, amid acclaim from his supporters, a day before his mandate expires without a designated successor, threatening a new power vacuum in the crisis-torn country.

A few thousand well-wishers gathered to pay tribute to the Maronite Christian former army chief and head of the Free Patriotic Movement which is allied with the powerful pro-Iranian Shiite movement Hezbollah.

FPM supporters, some brandishing portraits of the outgoing head of state widely referred to as "General", flocked to the presidential palace in the hills above the capital Beirut, where some had spent the night in tents, to accompany him to his private home.

"We have come to escort the president at the end of his mandate, to tell him that we are with him and that we will continue the struggle by his side," said teacher Joumana Nahed.

Lebanese lawmakers have tried but failed four times in a month to agree on electing a successor after Aoun's six-year term ends Monday, stoking fears of a deepening political crisis.

The term of Aoun, who is in his late 80s, was marred by mass popular protests, a severe economic crisis and currency collapse, and the August 2020 portside blast of ammonium nitrate that killed hundreds and laid waste to swathes of the capital.

Neither the Hezbollah camp, the powerful armed movement which dominates political life in Lebanon, nor its opponents have the clear majority to impose a candidate to succeed him.

Lebanon is being run by a caretaker government as political divisions have prevented the formation of a new cabinet ever since legislative elections in the spring.

This comes at a time Lebanon has yet to enact most of the reforms required for it to access billions of dollars in loans from the International Monetary Fund.

Some at the palace Sunday recalled previous turbulence in the country that was torn by the bloody 1975-1990 civil war and decades of military intervention by neighbour Syria.

Nabil Rahbani, 59, said he had camped outside the presidential palace once before, "between 1989 and 1990, before the Syrian air force dislodged the general from Baabda Palace".