Shiral Lakthilake, a member of the western provincial council, said senior United National Party (UNP) leaders were attacked by the mobs "using petrol bombs, swords, daggers and clubs."

"Senior police officers were mere witnesses while the mobs were attacking us in Borella" he told BBC Sinhala service, Sandeshaya.

He said the UNP deputy leader Karu Jayasuriya and general secretary Tissa Attanayake were among those came under attack.

The opposition accused the police of not taking any action to prevent the attack.

The protest organised by the UNP were marching towards Welikada prison where former army commander Sarath Fonseka is kept.

The UNP boycotted the independence day celebrations held in Kataragama, southern Sri Lanka, protesting against the jail sentence imposed upon the former military commander.

Mr Fonseka is regarded by many as the main architect of government's war against the Tamil Tigers.

Mr Lakthilake said the protesters identified many of the attackers as pro-government mobs who had taken part in previous attacks against the opposition.

"Many people were injured and the vehicle belong to Dayasiri Jayasekara, MP, was also badly damaged," he said.