Robert Fisk: Opposition demonstrations turn Beirut into a violent sectarian battleground

So the worst nightmare years may have begun again. There were thousands of them - Christians fighting Christians north of Beirut, Sunni and Shia Muslims in the capital, a rain of stones, shrieks of hatred and occasionally even gunfire - that turned Lebanon into a sectarian battleground yesterday.

At the corner of a street off Corniche al-Mazraa, I watched what historians may one day claim was the first day of Lebanon's new civil war, huge mobs of young men, supporters and opponents of Fouad Siniora's government screaming abuse and throwing tens of thousands of rocks at each other as a wounded Lebanese soldier sat next to me and wept.

For the army of this tragic country is now the thin red line ­ some actually were wearing red berets ­ that stands between a future for Lebanon and the folly of civil conflict.

After 31 years in this country, I never truly believed I would see again what I witnessed on the streets of Beirut yesterday, thousands of Shia and Sunni Muslims, the first supporting the Hizbollah, the second the government once led by the murdered ex-prime minister Rafik Hariri, hurling stones and hunks of metal at each other. They crashed down around us, smashing the road signs, the advertisement hoardings, the windows of the bank against which seven Lebanese soldiers and I were cowering. Again and again, the soldiers ran into the roadway to try ­ with a desperation all of them understood, and they were brave men ­ to drag the youths from each other. Some of the Shia men, Amal members, loyal (heaven spare us) to the Speaker of Parliament, wore hoods and black face masks, most wielding big wooden clubs.

Their predecessors ­ perhaps their fathers ­ were dressed like this 31 years ago when they fought in these same streets, executioners-to-be, all confident in the integrity of their cause. Perhaps they were even wearing the same hoods. Some of the troops fired into the air; they shouted at the stone throwers. "For God's love, stop," one young soldier screamed. "Please, please."

But the crowds would not listen. They shrieked "animals" at each other and obscenities and on one side of the street they produced pictures of the Hizbollah leader, Hassan Nasrallah, and of Michel Aoun, the Christian ex-general who wants to be president and is Nasrallah's ally, and on the other side of the street, the Sunnis produced a portrait of Saddam Hussein. Thus did the cancer of Iraq spread to Lebanon yesterday. It was a day of shame.

Across Lebanon came reports of dying men ­ two according to one, six according to another, and at least 60 wounded ­ and the country's leaders were last night writing their narrative of Lebanon's modern history with predictable speed. Nasrallah, hero of last summer's war with Israel ­ or so he likes to think ­ demanding the resignation of the government while Siniora and his colleagues, trapped in the old Turkish "serail" downtown, called this an attempted coup d'état by the forces of Syria and Iran.

It is not that simple. The Shias are the downtrodden, the poor, the dispossessed, those who have always been ignored by the dons and patriarchs of the Lebanese government ­ for in one sense this is also a social revolution ­ and on the other were the Sunni population so beloved of Hariri and the Druze and the Christians still loyal to the Lebanese forces who were Israel's allies in 1982 and who massacred the Palestinians in the camps of Sabra and Chatila, as well as a majority of Lebanese innocents who voted Siniora's government into power.

Thus north of Beirut, Aoun's Christian forces tried to block the roads and were set on by Samir Geagea's thugs. In Tripoli, supporters of Hariri's son Saad were fighting Alawite supporters of Syria. In Hazmiyeh, it was Shias versus Christians and in Corniche al-Mazraa, it was Shias against Sunnis. No, as Nasrallah would be the first to say, this is not necessarily a civil war ­ and it has to be said that the Hizbollah's tens of thousands of fighters were by far the most disciplined men on the streets of Beirut ­ but it was he who called a general strike yesterday on the eve of the Paris economic conference that is supposed to save Lebanon's economy and who blocked all the main roads of Lebanon with burning tyres and concrete blocks and pipes and rubble from last summer's war.

My driver, Abed, and I tried to reach the airport but vast swaths of black smoke poured from the burning rubber on all the approach roads. I walked three miles to the terminal, only to find the Hizbollah protecting both the airport and the Lebanese troops who were guarding it. When we turned round, Abed tried to drive over the burning tyres but trapped one beneath our car, the flames curling up the sides of the bodywork, desperately reversing to clear our wheels as Hizbollah men screamed abuse.

Siniora condemned it all last night, demanding an emergency session of parliament. He still plans to go to the Paris summit. But how will he get to the airport? "We will not be scared," Nasrallah said yesterday. "We will not retreat ... We will not be dragged on to the streets [of civil war]." But he should have been on Corniche al-Mazraa. All across Beirut, the Hizbollah, most dressed in black trousers and shirts (for this is the holy month of Ashura, is it not?) had closed the roads, and the army stood and watched. It is a largely Shia army, for it is the Shias who are the largest community in Lebanon, but in the streets they were forced to fight. As I sat with the soldiers amid the crashing stones ­ many of the projectiles hurled into the street from the roofs of eight-storey apartment blocks ­ I watched them wilt under the pressure. One knelt down and vomited; others were almost overcome by their own tear gas, fired uselessly at the vast crowds. For these were not Belfast-sized riots or Gaza-sized demonstrations.

The mobs were there in their thousands, chorusing their hatred for those who lived across the other side of the boulevard. There were few officers. But after an hour, a Lebanese colonel ran down the street, a smartly dressed man, not even wearing a flak jacket, who walked straight into the highway between these two great waves of angry people, the stones banging off his helmet and body and legs. And the soldiers around me stood up and ran into the road to join him between these two enormous forces.

I don't like journalists who fall in love with armies. I don't like armies. But yesterday it seemed that this one man was a lonely symbol of what stood between Lebanon and chaos. I don't know his religion. His soldiers were Sunnis and Shias and Christians ­ I had checked, of course ­ all dressed in the same uniform. Could they hold together, could they remain under his command when their brothers and cousins, some of them, must have been among the crowds? They did. Some even grinned as they hurled themselves at the hooded men and youths too young to have known the last civil war, pleading and shouting for the violence to end. They won. This time. But what about today?