Two Syrian refugee children in Lebanon suffocated to death overnight in a fire started by a lit candle during a power outage, Lebanon's state news agency reported on Friday.

Ahmed, just three years old, and his four-year-old sister Mona, were staying with their parents in a home in Kafr Ruman in southern Lebanon.

The family had lit candles overnight during one of the country's frequent electricity cuts, the National News Agency said.

"The room they were sleeping in caught on fire and they suffocated to death," the agency reported, saying a third sibling, Mohamed, was taken to hospital suffering burns.

"Their parents, who were outside the house, were told what was happening by neighbours and returned home. They were taken to hospital suffering nervous breakdowns," the agency added.

More than 600,000 Syrians have taken refuge in Lebanon, fleeing the conflict in their country, which is now in its third year.

Unlike in Jordan and Turkey, no refugee camps exist in Lebanon for those escaping Syria, and many refugees have been forced to seek shelter in single rooms or makeshift homes.

Others have ended up sleeping in the streets in the country's cities, many forced to beg to get by.

More than 100,000 people have been killed in the Syrian conflict, which began with peaceful anti-regime protests in March 2011, before devolving into a full-fledged war.

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