A dispute between the Electricity of Lebanon (EDL) and its day labourers demanding their tenure led to the national security company to warn on Tuesday that the entire country could be blacked out.

"The company is obliged to close its doors" due to the "occupation of its headquarters by day labourers," EDL said in a statement late on Monday.

"This decision will result in an electricity blackout throughout Lebanon in a matter of hours," EDL warned, calling on citizens, most of whom already have generators, to take "precautionary measures."

Some areas of Beirut were without power beyond the usual hours of rationing beginning Monday evening and continuing into Tuesday.

An AFP photographer said that striking labourers blocked entrances to the company headquarters on Monday.

They rejected the claims of EDL that their actions had impaired operations at power stations.

The workers insisted the strike was limited to bill collection and that power station employees "continue to work normally."

Day labourers at the public company have been demanding their tenure for years and have held a sit-in for weeks. Electricity bills have not been collected for at least three months.

EDL warned that the decision to close its doors would remain in effect until the end of the strike, but labourers have refused to budge.

In a country where several Muslim and Christian communities coexist, the dispute has taken on a religious dimension: labourers are mainly Shiite, while Christian parliamentarians united in opposition to a bill advocating their tenure.

The law was passed in July, but never went into effect, with Christian politicians citing a religious imbalance at the public company.

Chronic power shortages since the end of Lebanon's 1975-1990 civil war have been a main source of grievance among Lebanese who have had to put up with daily cuts.

Apart from the lack of investment, theft of electricity and attacks against collectors are common in many areas.

Electricity output in Lebanon reaches 1,700 MW on average in the summer at a time when the demand stands at 2,500 MW.