Several people were injured in the blast

Saturday's blast was caused by a small amount of dynamite hidden in the toilet of the restaurant in Dora, a Christian district of Beirut.

Police later found a car filled with 55 kilograms of TNT in a nearby car park.

The car did not explode because of failures in two of the three detonators, police said.

This "saved the district from a catastrophe", a police official said.

No group has said it carried out the attack.

It is the fourth on an American fast food outlet since early March - but the first to occur at a time when the restaurant was bound to be full.

The other attacks - which occurred at night or around dawn - have hurt no one.

Series of incidents

On 24 March, a small bomb went off at a British cultural centre in Beirut but caused no injuries.

Last week, a man stormed into a British bank in Beirut with explosives strapped to his body, threatening to detonate himself before he gave himself up to police.

In November, an American nurse was shot dead at a clinic in the southern Lebanese city of Sidon where she worked.

American businesses and western embassies in Lebanon have been given armed guards by internal security forces since the start of the Iraq crisis.

The US embassy has urged American citizens to leave Lebanon.

The Lebanese government is opposed to the US-led war on the Iraq.

Beirut has seen almost daily anti-war demonstrations and calls for boycotts of American products.