Hizbollah fighters spread virtually unopposed across west Beirut districts loyal to the pro-Western government.

After a night of firefights, the mainly Sunni Muslim residents of the capital's west woke to find Shia Hizbollah fighters patrolling the streets.

The main compounds of country's two senior political leaders were besieged in a dramatic demonstration of the shift in power.

Interspersed among the masked and heavily-armed fighters on Friday were political operatives who exercised a calm but wary control.

"You are welcome but it is dangerous here. Be very careful," a bearded commander, fingering a Kalishnikov rifle, said.

"Do not take any photos of anybody, not even their backs, nothing. This is an orderly response but we cannot guarantee your safety."

From their barricaded homes, residents described a night during which the sound of thunderstorms mixed with grenade explosions and the automatic gunfire.

"It was terrifying," said one woman.

"We couldn't even move about in the house. We spent the night in the corridor."

Thirteen people were reported killed as sporadic clashes continued throughout the day.

The beleaguered government of prime minister Faud Sinioria accused Hizbollah of mounting an armed coup with the aim of restoring Syria's dominant position in Lebanese affairs.

Syria, Iran's only Arab ally, was forced to withdraw its army from Lebanon in 2005, ending 15 years of control of Lebanese politics from Damascus.

"The armed and bloody coup which is being implemented aims to return Syria to Lebanon and extend Iran's reach to the Mediterranean," said Samir Geagea, the Christian faction leader.

International condemnation of Hizbollah focused on the potential for the crisis to spill across the borders.

Shimon Peres, the Israeli president, pointed to Hizbollah's links with Iran's Islamic regime.

He said: "It is a new chapter of the battle led by Iran to control all of the Middle East."

The Iranian-trained and financed Shia faction fought Israel to a standstill in 2006 after triggering an invasion.

Hassan Nasrallah, the Hizbollah leader, said that Lebanon had entered a "new era" following government efforts to wrest control of the airport from the terror group.

He accused the government of working on behalf of the CIA and Israeli intelligence.

Saad Hariri, the political heir of the assassinated former Lebanese prime minister Rafik Hariri, was on Friday trapped in the family compound surrounded by Hizbollah.

Syrian-backed allies of Hizbollah set fire to a television station owned by the family.

The White House said it was "very troubled" by events in Lebanon.

The Arab League called a meeting of foreign ministers in Cairo on Sunday to find a way to defuse the tensions but the meeting is likely to see renewed clashes between Saudi Arabia and Syria.

The Foreign Office urged British citizens to cancel any plans to visit the country.

Thousands mobbed border crossings with Syria but other routes in and out of Lebanon, including the airport and ports, were shut.