Eight political parties set to contest in the July 28 polls began a month-long election campaign on Thursday.

Three major parties among them are the ruling Cambodian People' s Party (CPP), the opposition Cambodia National Rescue Party, and the royalist Funcinpec Party.

The ruling party launched its campaign with about 20,000 supporters, gathering at the capital's Diamond Island Center. The party's leaders,including President of the Senate and Party's President Chea Sim, President of the National Assembly and Party's Honorary President Heng Samrin, and Prime Minister Hun Sen, the Party's vice-president, were present at the rally to encourage their supporters.

After the rally, the activists proceeded through main roads in the city by motorcycles and cars that were equipped with loudspeakers and decorated with the party's logos, flags and banners.

The country's opposition Cambodia National Rescue Party, led by self-exiled leader Sam Rainsy, began its campaign at the capital's Freedom Park with about 5,000 members. Kem Sokha, Party's vice president, led the campaign, according to Ho Vann, deputy chief of the party's disciplinary committee.

While the royalist Funcinpec Party, headed by Princess Norodom Arun Rasmey, the youngest daughter of late King Father Norodom Sihanouk, held a rally in eastern Kampong Cham province.

The party's Secretary General Nhek Bun Chhay said that some 5, 000 supporters attended the rally and marched through the provincial town to spread the party's political platform.

He said the party launched the campaign in Kampong Cham province because Princess Norodom Arun Rasmey is a candidate in the province.

Security forces have been deployed among streets to ensure security and public order during the one-month campaign.

Lt. Gen. Kirt Chantharith, spokesman for the National Police, said Wednesday that about 20,000 and up to 70,000 members of the security forces would be deployed during the campaign and the election day.

According to the National Election Committee, some 9.67 million Cambodians are eligible to cast their ballots for the 123-seat parliament on July 28.

In the last election in 2008, Prime Minister Hun Sen's party won up to 90 seats, while the opposition won 29 seats, and the royalist group got four seats.

Political analysts predict that Hun Sen's party will win a landslide victory in the upcoming polls.

Hun Sen, 61, has been in power for 28 years and vowed to stay in the post until he is 74.