Drilling off Lebanon's coast has detected traces of gas but no commercially viable reserves, the energy minister and an exploration firm said on Monday.

"Initial drilling results showed the presence of gas at different depths in the geological layers" of block 4, Energy Minister Raymond Ghajar told reporters at a news conference.

But after some two months of drilling "no gas reservoir, no commercial reservoir was found," he said.

The results had been awaited with anticipation, with many Lebanese hoping a major hydrocarbon discovery could help redress the debt-burdened economy.

A consortium composed of energy giants Total, Eni and Novatek was awarded the first two of Lebanon's 10 exploration blocks in 2018 -- block 4, and block 9 near the Israeli border.

French oil firm Total confirmed the poor outcome for the first ever exploration well off the Lebanese coast in block 4.

"Despite the negative result, this well has provided valuable data and learnings that will be integrated into our evaluation of the area," Total's Lebanon managing director Ricardo Darre said in a statement.

Results from block 4 are needed to finalise a strategy on how best to probe block 9, where Ghajar said drilling would start as soon as possible.

Exploration of block 9 has been more controversial as Israel also claims ownership of it.

In the past, Total has said it was aware of a border dispute affecting less than eight percent of block 9 and would drill away from that area.

Lebanon is one of the most indebted countries in the world, with a burden equivalent to 170 percent of its gross domestic product.

It is grappling with its worst economic crisis since the 1975-1990 civil war, now compounded by a nationwide lockdown to stem the spread of the novel coronavirus.