Thousands of people gathered in central Beirut today for the funeral of an assassinated senior intelligence officer, accusing Syria of involvement in the killing and calling for Lebanese prime minister Najib Mikati to quit.
Lebanon's opposition leader Saad al-Hariri urged supporters to pull back after protesters tried to storm the offices of Mr Mikati.
"We want peace, the government should fall but we want that in a peaceful way. I call on all those who are in the streets to pull back," Mr Hariri told supporters through Future Television channel.
US Secretary of State Hillary Clinton spoke to the Lebanese prime minister today to reiterate US condemnation of Friday's deadly car bombing in Beirut, and the two agreed that Washington would help investigate the attack.
In a phone call with Mr Mikati, Ms Clinton called the attack that killed intelligence chief Brigadier General Wissam al-Hassan and others "heinous" and offered condolences, State Department spokesperson Victoria Nuland said.
"The secretary emphasized the United States' firm commitment to Lebanon's stability, independence, sovereignty and security," Ms Nuland said in a statement.
"She noted the importance of political leaders working together at this sensitive time to ensure that calm prevails and that those responsible for the attack are brought to justice."
However as night fell in Beirut groups of youths blocked the road to the international airport with piles of burning tyres. The highway south to Sidon was also cut.
Former prime minister Fouad al-Siniora, who is from Hariri's party, said "any attempts to storm the Saray (government offices) is unacceptable."
Heavily armed troops and police stood guard as people flocked to Martyrs' Square in central Beirut.
Many waved the sky-blue flag of the Sunni-based opposition Future Party. Others carried Lebanon's cedar tree national flag but Syrian rebel flags were also seen.
One banner read "Go, go Najib" echoing the slogans of the Arab Spring.
Brigadier General Wissam al-Hassan was killed by a powerful car bomb in Beirut's Ashrafiyeh district on Friday. A Sunni Muslim close to the Hariri political clan, he had helped uncover a bomb plot that led to the arrest and indictment in August of a pro-Damascus former Lebanese minister.
He also led an investigation that implicated Syria and its Lebanese ally Hezbollah in the assassination of former prime minister Rafik al-Hariri in 2005.
Lebanese politicians have accused Syria's leadership of having a role in Mr Hassan's killing, which deepened fears the civil war there is spreading over its borders.
People in the crowd at Martyrs' Square echoed that view.
"We blame Bashar al-Assad, the president of Syria," said Assmaa Diab (14), from the northern city of Tripoli, Mr Hassan's hometown. She was in the square with her sister and father.
"He is responsible for everything - in the past, now, and if we don't stand up to him, the future," she said.
The prime minister was also a focus of their anger.
Diab and other protesters said they wanted him to step down, saying he was too close to Shia Hezbollah, who are part of his government, and to Dr Assad.
"We are here to tell Mikati we don't need him any more and to tell Hezbollah we don't want any more of their games," said Hamza Akhrass, a 22-year-old student who had come from south Lebanon for the funeral.
"Mikati takes too much pressure for Syria." One banner read "People want the overthrow of Najib".
Mr Mikati said yesterday he had offered to resign to make way for a government of national unity but he had accepted a request by President Michel Suleiman to stay in office to allow time for talks on a way out of the political crisis.
The 19-month-old uprising in Syria against Assad has exacerbated deep-seated sectarian tensions in Lebanon, which is still scarred from its 1975-90 civil war.
Sunni-led rebels in Syria are fighting to overthrow Assad, who is from the Alawite minority, which has its roots in Shia Islam. Lebanon's religious communities are divided between those that support Assad and those that back the rebels.
Mr Mikati sought in vain to insulate the country from turmoil in its larger neighbour, which has long played a role in Lebanese politics.
Today's funeral march set off from Mr Hassan's Internal Security Force headquarters in Ashrafiyeh and will pass the site of Friday's bombing before reaching Martyrs' Square where he will be buried alongside slain prime minister Hariri.
Mr Mikati himself said he suspected Hassan's assassination was linked to his role in uncovering Syrian involvement in the August bomb plot.
Reuters