Metropolitan Police Division VI deputy commander Colonel Supisal Pakdeenarunart said the 26 vendors would be charged with holding an illegal gathering of more than 10 people, blocking traffic, causing a disturbance, obstructing officials in their duties and refusing to obey officials' orders.

If convicted, they face up to three years in jail.

The arrests were made after members of a crowd of about 2,000 protesters began hurling abuse, water bottles and chairs at police officers. Commando policewomen were deployed to arrest women demonstrators.

The protest began at 7.30pm on Thursday over the parking of seven Bangkok Metropolitan Administration (BMA) garbage trucks and toilet trucks alongside the footpath along the Padung Krungkasem Canal in the heart of Bangkok.

Vendors with stalls on the footpath, which form part of the Bo Bae market, were unhappy about being obstructed by the trucks, which have been parked there since a big fire at the Bo Bae Market on December 29.

The vendors set up tents at a nearby intersection, blocking traffic and causing severe congestion on roads in the area, and demanded negotiations with Bangkok Governor Apirak Kosayodhin.

The some 600 policemen present could not stop the vendors from moving onto the road because there were women and children at the front of the crowd that pushed against the shield-carrying officers.

By yesterday morning the protest had paralysed traffic to such an extent that many adjacent areas were seriously affected.

At 8.30am the police announced that they would use harsh measures if the demonstrators refused to clear the way for traffic.

The demonstrators finally did so at 10am but continued with a sit-in protest on the footpath.

The BMA then sent backhoes to the spot to start on its plan to landscape the footpath. The sight of the backhoes angered the demonstrators, some of whom began hurling abuse, chairs and water bottles at the police, prompting the arrests.

Police managed to disperse all the demonstrators and take control of the footpath by 1.30pm.

The BMA earlier announced plans to move the stalls from the footpath but was met with strong opposition from the vendors, who have been operating there for more than 20 years.

Sak Silapacharoenporn, one of the vendors, complained that he had operated his stall on the footpath for more than 20 years and had never had any problem under previous Bangkok governors.

"The BMA has told us to relocate to another spot, but that spot is crowded, and I will be asked to pay Bt200,000 to Bt300,000 for the lease there. How can I afford it?" the 52-year-old vendor said.

Kriang sae Tang, an assistant at one of the stalls, said she would lose her job now that her employer did not have a space to operate the stall.

"Why did the authorities do this to us? We have already suffered a lot. There was a big fire, and now there will be no stalls for us," she said tearfully.