Cambodia's opposition has threatened huge protests if concerns over the fairness of last month's general election are not dealt with.
Sam Rainsy, the leader of the Cambodia National Rescue Party, told thousands of supporters on Monday in the capital Phnom Penh that an independent committee should investigate alleged irregularities.
The official results give Prime Minister Hun Sen's Cambodian People Party 68 national assembly seats against 55 for the Rainsy's party. Rainsy says it would have won 63 seats if the election was fair.
The opposition alleges omission of more than one million people from the voters list. Several non-partisan poll watching groups support that claim.
Hun Sen, who has been in power for 28 years, moved troops and armoured vehicles into the capital after the opposition first threatened protests several weeks ago.
A compromise would be in Hun Sen's interests to give his regime legitimacy, especially among Western nations that have raised questions about the fairness of the polls.
The country's highest court, the Constitutional Council, has started reviewing the July 28 poll results, leaving open the possibility that the opposition's concerns can be resolved.
The council has up to 20 days to complete its review.