PHNOM PENH (Reuters) - More than half-a-million spoilt ballots in Cambodia’s general election represent a protest against the vote that critics have called a sham, the opposition and an analyst said on Monday.

FILE PHOTO: Officials begin the process of counting ballots after polls have closed in Cambodia's general election, at a polling station in Phnom Penh, Cambodia, July 29, 2018. REUTERS/Darren Whiteside

Prime Minister Hun Sen’s ruling Cambodian People’s Party (CPP) has said it won all 125 parliamentary seats up for grabs at Sunday’s election, held without the main opposition Cambodia National Rescue Party (CNRP), which was dissolved by a court, and had its leader, Kem Sokha, jailed on treason charges.

As many as 594,843 votes, or 8.4 percent, of the 7.64 million votes cast, were invalid and spoiled, figures from the National Election Committee showed.

By comparison, spoiled ballots in the last election, in 2013, comprised just 1.6 percent of the total.

“It is a significant vote of disapproval of this particular election and an act of defiance of the unlawful coercion on voters to go to vote,” Cambodia-based political analyst Lao Mong Hay told Reuters.

“A cunning yet legitimate protest against the powerful.”

Government spokesman Phay Siphan said the large number of invalid votes showed an anti-election trend.

“They are anti-election and the Cambodian People’s Party,” Phay Siphan told Reuters.

During Sunday’s vote counting in Phnom Penh, the capital, a Reuters journalist saw numerous ballots that had been ticked all over, while other ballots were left blank.

Nineteen little-known parties contested against the ruling party, but none are particularly critical of it or the government.

Exiled leaders of the CNRP had called for a boycott of the vote, prompting the government to warn that anyone who did not participate would be seen as a “traitor”.

“We praise the courage of all voters who came out to mark their strong message by spoiling their ballots as their way of rejecting the sham election and those who stayed home and kept their fingers clean,” CNRP vice president Mu Sochua told Reuters, referring to the ink-mark that denotes a vote cast.

Rights groups accused the CPP of coercing citizens to vote for the ruling party, leaving many no choice but to spoil their votes in protest.

The White House said it would consider steps, including wider visa curbs on some members of the Cambodian government, in response to the “flawed elections”.