Cambodia's electoral campaign has been biased in favour of Prime Minister Hun Sen's Cambodian People’s Party (CPP), Human Rights Watch said, as political parties hit the streets in a final push for votes in Sunday's general election.
The CPP is widely expected to win another comfortable majority in the National Assembly.
Hun Sen has been prime minister for 28 years, bringing stability after years of war and the genocidal regime of the Khmer Rouge in the late 1970s. However, critics say he has shown disdain for democracy through intimidation of opponents and electoral fraud.
In a statement on Friday, the US-based HRW listed a series of problems that had marred the campaign, which officially ends at midnight on Friday.
HRW said unequal access to media for the opposition, the manipulation of voters lists and campaigning by officers of the security forces for the ruling CPP were among the problems it found.
"The entire process is biased in favour of the ruling party and against the opposition. What should result in the will of the people has been organised to result in the will of the Cambodian People's Party," said Brad Adams, HRW's Asia director.
The opposition leader, Sam Rainsy, returned home from self-exile last week after a royal pardon removed the threat of a jail sentence, but the electoral authority had still ruled he could not run in the election or even vote.
"An election with the leader of the opposition banned on spurious grounds is almost the definition of an unfair and undemocratic process," Adams said.
Reporting from the capital Phnom Penh, Al Jazeera's Scott Heidler said nobody expects a change in leadership but added that the hope lies in just how many seats the opposition will pick up.
Sam Rainsy's eponymous party merged with another last year to form the Cambodia National Rescue Party (CNRP). It is hoping to improve on the 29 seats the two parties held in the outgoing parliament. The CPP had 90 of the 123 seats.
"People here are sending a message to the current leaders that it's time for them to step down," Sam Rainsy told supporters in a Phnom Penh park.
"They should be ashamed of themselves and leave before they are chased out."
Hun Sen, who heads the governing party, has not made one speech during the month-long campaign period.
Rainsy, a former finance minister, has promised to increase wages in the garment sector, Cambodia's main export earner built on low pay, and provide free health care for the elderly.
The opposition leader said he would also put an end to "land grabs" in the countryside, where allies of Hun Sen and some foreign companies have been accused of stealing land from farmers.
Hun Sen and his CPP rose to power with the help of the Vietnamese army which invaded the country in late 1978 to oust the Khmer Rouge and then occupied Cambodia for a decade.