Lebanon's Iranian-backed Hizbullah group took control of the Muslim half of Beirut today in what the US-backed governing coalition described as "an armed and bloody coup".
At least 18 people have been killed and 38 wounded in three days of battles between pro-government gunmen and fighters loyal to Hizbullah, a Shi'ite political movement which has a powerful guerrilla army and is an ally of Syria and Iran.
The violence was a dramatic escalation after 17 months of political deadlock between the Hizbullah-led opposition and the government which has paralysed the country and left it without a president since last November.
The fighting, the worst internal strife since the 1975-90 civil war, erupted this week after the government decided to dismantle Hizbullah's military communications network. The group said the government had declared war.
In scenes reminiscent of the darkest days of the civil war, young men with assault rifles roamed the streets amid smashed cars and smouldering buildings.
Fighting died down as outgunned government supporters handed over their weapons and offices to the army, which has tried to remain neutral in the conflict.
The anti-Syria governing coalition condemned the "armed and bloody coup", saying it was aimed at increasing Iran's influence and restoring that of Syria, forced to withdraw its troops from Lebanon in 2005.
A White House spokesman said: "The United States is consulting with other governments in the region and with the UN Security Council about measures that must be taken to hold those responsible for the violence in Beirut accountable."
The White House restated its support for the government and urged Iran and Syria to end their support for Hizbullah, whose followers brought large parts of Beirut to a standstill this week with roadblocks.
"This support is a reflection of our unshakable commitment to the Lebanese people and their hope for democratic change," US Secretary of State Condoleezza Rice said.
"We will stand by the Lebanese government and peaceful citizens of Lebanon through this crisis and provide the support they need to weather this storm."
An influential pro-government leader called for dialogue.
Walid Jumblatt, leader of the Druze minority, said Hizbullah "regardless of its military strength, cannot annul the other".
"Dialogue alone brings results. Running away from dialogue is not useful," he told the pro-government LBC television.