Cambodia's opposition claims election win
Cambodia's opposition party says it narrowly won Sunday's general election, challenging the ruling party's earlier declaration of victory.
Hours after the poll, PM Hun Sen's ruling party said it won 68 seats in parliament to the opposition's 55.
But opposition leader Sam Rainsy said the result was 63-60 in his favour, and called for an independent commission to investigate poll irregularities.
Official poll results are not expected until mid-August.
Hun Sen has been in power in Cambodia for nearly three decades. The national election commission is widely expected to back his Cambodian People's Party (CPP), says the BBC's Jonah Fisher in Bangkok.
But the opposition Cambodia National Rescue Party (CNRP) says it does not accept the results. Earlier this week, it cited multiple irregularities with voter lists.
Human Rights Watch echoed the CNRP's concerns in a statement released on Wednesday.
"Senior ruling party officials appear to have been involved in issuing fake election documents and fraudulently registering voters in multiple provinces," said the organisation's Asia director, Brad Adams.
Sam Rainsy told the BBC that the opposition would not take its seats in parliament, which is expected to meet in September, until its win was recognised. This would also prevent a new cabinet being approved.
"We expect the CPP to concede the election to us. The information we have received from the our activists and party agents show that we have won 63 seats and they have won 60," he said.
"To move forward without an independent committee is cheating. We will comply with the conclusions of an independent committee. There is no other way or else the county will face a period of instability and uncertainty."
Ouch Borith, Cambodia's secretary of state at the Foreign Affairs Ministry, on Tuesday rejected claims of voting irregularities.
"We have over 10,000 national observers and over 100 international observers who reckoned our election was held in a peaceful manner without any violence, free and fair," he said.
Both the US and the European Union have expressed concern over the conduct of the polls and have asked the election commission to conduct an investigation.
"We are concerned by numerous reported irregularities in the electoral process," US State Department spokeswoman Jen Psaki said on Monday.
She added that Washington had long highlighted "systematic flaws such as problems in the voter registry and unequal access to the media".
The result announced by the CPP represented the worst result for the ruling party in 15 years.