BBC Correspondent in Phnom Penh, Caroline Gluck: "This was a monument built to symbolise friendship"

At one stage, a section of the crowd attacked a statue erected by the Vietnamese when they occupied Cambodia after the overthrow of the Khmer Rouge.

The statue was smashed with hammers and daubed with paint.

It was also sprayed with slogans attacking the incumbent Prime Minister Hun Sen - who won last month's election.

Hun Sen rose to power in the Vietnamese-backed government during the 1980s.

Opposition politician Sam Rainsy: "The protest is completely legal"

Prominent opposition politician Sam Rainsy, who has spearheaded the demonstrations, has labelled Hun Sen a puppet of Vietnam, Cambodia's traditional enemy.

Unprecedented protest

Demonstrators threw paint and petrol at the monument

During the latest demonstrations, people marched through the streets of Phnom Penh to join other crowds at the unprecedented round-the-clock vigil outside parliament.

The government has not intervened in the protest, wary of provoking the crowds.

However the Secretary of State for Information, Khieu Kanharith, said plans were being made to take legal action against the Sam Rainsy.

UN call for restraint

On Saturday, the United Nations called for restraint from both the Cambodian Government and opposition parties.

Protestors denounce incumbent Prime Minister Hun Sen

The UN special representative for human rights in Phnom Penh, Thomas Hammarberg, said he was concerned by statements that might incite violence, particularly against ethnic Vietnamese.

He urged everyone to exercise restraint, to ensure that people could exercise their right of freedom of assembly.

Sam Rainsy and Cambodia's deposed First Prime Minister, Prince Norodom Ranariddh, have criticised last month's elections.

They have demanded a caretaker government and a neutral prime minister to run the country ahead of fresh elections.

Prince Norodom Ranariddh: "International community should look at the will of the people"

Hun Sen's Cambodian People's Party (CPP) won the most votes in the July election, but with a majority that was insufficient to form a government on its own.