While there were few reports of casualties, the scale of sectarian fighting has not been seen since the civil war ended in 1990.

The crisis erupted after the American-backed Sunni government removed the airport's head of security, accusing him of tolerating a Hezbollah spying operation.

Hassan Nasrallah, Hezbollah's leader, in his first public appearance since the eve of its 2006 war with Israel, said: "The decisions are tantamount to a declaration of war and the start of a war on behalf of the United States and Israel."

He added that the government was planning to hand control of the airport to CIA or the Israeli secret service.

"We are not seeking war with anyone, but the government must go back on its decision and we are being patient." He told the Lebanese people: "You are with us or against us."

Flights were cancelled for a second day after Hezbollah cut access, setting up barricades of burning tires and rubble.

Hezbollah was condemned as a threat to regional stability by the United Nations envoy Terje Roed-Larsen at an emergency meeting of the Security Council in New York. He said its paramilitary infrastructure was "adverse" to government control, and said the group "constitutes a threat to regional peace and security".

"We remain gravely concerned about the potential for further escalation," he said. "The secretary-general urges all parties to cease immediately these riots and to reopen all roads in the country."

America's UN ambassador, Zalmay Khalizad, called for the UN to consider sanctions on Syria, an ally of Hezbollah, if the fighting spread.

He said that without those kinds of developments, the council "will have to confront these challenges and deal with the problem by taking appropriate steps".