Cambodian authorities have refused to give permission to the opposition-aligned trade unions and associations to hold a public forum at the capital's Freedom Park on Saturday.

"The Phnom Penh Municipality does not allow the 18 trade unions and associations to hold the public forum on March 8 at the Freedom Park or other public places because this forum's purpose has mixed with political characteristics," said a letter signed by Phnom Penh Vice-Governor Khuong Sreng and sent to those trade unions and associations late Thursday.

"In the meantime, the ruling Cambodian People's Party (CPP) and the opposition Cambodia National Rescue Party (CNRP) have subsequently met and discussed electoral reforms, so the ban is to give time to the two political parties to continue their negotiations in a better atmosphere, especially to avoid affecting security, safety and public order for the people," the letter said.

However, the letter allowed those unions and associations to hold the forums at their respective offices.

Pav Sina, president of the Collective Union of Movement of Workers, said Friday that the 18 opposition-aligned trade unions and associations would go ahead with the forum schedule at the Freedom Park on Saturday despite permission denial from the City Hall.

"We expect thousands of people will take part in the forum," he told Xinhua.

He said the forum's agenda included a demand for a 160 US dollars minimum wage for garment workers and a call for the release of 21 detained protesters.

On Thursday afternoon, more than 2,000 security forces received a special training at the capital's Olympic Stadium in preparation for any future demonstrations.

Gen. Chuon Sovann, chief of the Phnom Penh Municipal Police, said security forces will protect demonstrators if their demonstrations are legal, but if demonstrations are illegal, organizers must be responsible for any incidents.

Many protests have been staged by the opposition CNRP and its aligned trade unions since a disputed election in July last year that handed victory to Prime Minister Hun Sen's ruling party.

Two violent protests in early January had left four protesters dead and 21 others still detained.