The cause of the flames, which has spread from woods south of Beirut up to pine forests in the north, remains unknown, though some officials have blamed a heat wave that hit the country in recent days.

Lebanon's Red Cross said that 18 people have so far been hospitalised and 88 have received emergency medical care.

The fires have left charred trees and burned-out cars and have overpowered Lebanon's fire brigades, prompting appeals to neighhouring states to send aircraft to bolster efforts.

A civil defence official said 104 fires had broken out over the past 24 hours, and that residents had been evacuated from homes and buildings to minimise the toll.

"The fire was so strong it did not leave anything. It did not leave any greens, any buildings, anything," said Hussein Mcheik outside his home in the badly afflicted Mechref area south of Beirut.

Prime Minister Saad al-Hariri said an investigation would be opened and if arson were uncovered the perpetrators would "pay a price," though he said the fires might be the result of climate change, which often brings weather drier and hotter than normal.

So far Cyprus has sent helicopters and Greece has agreed to offer two aircraft, Interior Minister Raya al-Hassan said.

"We have contacted all the countries that can help us," he said.

Australian Associated Press