Strasbourg, France  - Many demonstrators came to march for peace, but instead there was violence as masked rioters unleashed an orgy of destruction in Strasbourg on Saturday, burning a hotel, a tourist bureau and a pharmacy.

The scene, the approaches to the Pont de l'Europe road bridge, was just a couple of hundred metres away from a footbridge over the Rhine River where President Nicolas Sarkozy had welcomed the other 27 leaders of NATO to a summit Saturday.

Smiles in the morning. Grim skirmishing in the afternoon.

The rioters hurled bottles and stones at police and petrol bombs into the buildings to set them alight. Another building to be burned was a vacant customs post, no longer used now that people and goods can pass without check between Germany and France.

A column of dark smoke rose hundreds of metres into the Strasbourg sky over the Pont de l'Europe, which was built to symbolize Franco- German friendship and crosses the Rhine, which is the historic line of defence between the two old rivals.

The original plan had been for tens of thousands of opponents of the NATO alliance to converge peacefully from both sides of the Rhine for a big rally to denounce what they perceive as NATO "war- mongering" in Iraq and Afghanistan.

But the violence overwhelmed the pacifist part of the crowd. The non-violent element were in shock and despair.

"You can't call that a demonstration," said a German woman, Giti, sadly. She had taken part in a non-violent demonstration against NATO the previous day in the German city of Baden-Baden and she insisted that peaceful demonstrators were the silent majority in the crowd.

"Now all these guys in ski masks have ruined everything. We won't be able to demonstrate today," she said, referring to the militants who wore the rioters' uniform: black jeans, black hoodies and ski masks to conceal their faces from police video cameras.

The French prefecture of Strasbourg estimated there were 1,000 violent demonstrators in the crowd.

Across the river in Strasbourg's German-territory suburb, Kehl, a procession by 7,000 anti-NATO demonstrators was banned from crossing the Pont de l'Europe to join the main rally in Strasbourg as planned.

The German police drew up water cannon just in case anyone tried to storm the bridge, and arrested anybody coming over from the French side wearing a ski mask. Police loudspeakers warned: "Stop attacking our police officers, or else we'll deploy water and riot clubs."

The day of marching had begun at dawn, when the first anti-NATO activists, who came from several nations, departed from their camp in the south of Strasbourg in multiple groups to try to find their way into the city through the police cordon.

In a cat-and-mouse game, tens of thousands of police charged with protecting NATO leaders meeting in the downtown area continually obstructed the activists, but they managed to block a tram line as well as a road to the conference venue.

Hundreds of activists lay down in the road, or danced on the tarmac, played musical instruments and chanted, "NATO no."

"Getting this far is quite a success," beamed one of their spokesman at a sit-in on the road.

Further to the south, grimmer clashes had already begun, with police firing tear gas, rubber bullets and sound-and-flash grenades.

Militants and police clashed for hours on the road leading to the Pont de l'Europe. Witnesses said the activists initially tried soft tactics, flashing smiles and waves and brandishing flowers at police, but were repelled with a volley of tear-gas grenades.

It was not long before the first stone was thrown at the police cordon and the violence escalated, with the militants taking up clubs and firing signal flares at the police. Petrol bombs began exploding with loud reports around noon.

By that stage 28 people had been arrested.

The protesters said several of their number were hurt by rubber bullets, but police did not confirm this.

German police charged that the pacifists were willingly acting as human shields to prevent police arresting militants in their midst.

By the afternoon, the youths in ski masks had fully taken over as the demonstration proceeded up the river bank.

In the area of the bridge approaches, the militants were practically unhindered by the police. They broke windows, smashed up a filling station, ripped down advertising hoardings and tipped over police riot barriers.

The fire in the five-storey hotel gutted the building. Sources told the German Press Agency dpa that the building was unoccupied on Saturday, but that the attackers apparently believed out-of-town police had been accommodated there overnight.

When French police, assisted by German units seconded over the bridge, counter-attacked and arrested some of the arsonists, the demonstration simply dispersed. The non-violent element had withdrawn much earlier.

The militants just ran away when the police began chasing them with water jets and tear gas.

For pacifists, who argued that they could confront NATO with non- violent methods, the outcome was an utter disappointment. (dpa)