The leaders of Cambodia's two main political parties held talks Saturday described as a step towards breaking the country's political deadlock following strongman Prime Minister Hun Sen's disputed election win.

While there was no major breakthrough at the rare meeting, hosted by King Norodom Sihamoni, opposition chief Sam Rainsy said that limited progress was made in ending the political paralysis gripping the kingdom.

He described the 30 minutes of talks, held at the royal palace in Phnom Penh, as a "first step" forward, without elaborating.

The king invited elected lawmakers to the first meeting of parliament on September 23 and asked the party leaders to continue their meetings, Rainsy said.

Hun Sen and the opposition chief were seen shaking hands in footage broadcast by state-run television.

Despite the tentative signs of a thaw, the deputy leader of Rainsy's Cambodia National Rescue Party (CNRP), Kem Sokha, indicated that the opposition had not dropped its planned boycott of parliament.

"Sam Rainsy already informed the king that the CNRP cannot accept the serious irregularities before and after the election. So the CNRP still insists on finding justice for the people," he said.

Leaders from the two main parties -- including Rainsy -- will hold further talks on Monday, he added.

It was unclear whether Hun Sen would personally attend.

With no deal yet struck, the opposition said it would go ahead with its planned demonstration on Sunday at the capital's Democracy Park.

Kem Sokha said the rally "will be bigger than before".

Anti-riot and military police were deployed at key locations in Phnom Penh on Saturday, according to an AFP reporter.

About 20,000 opposition supporters joined a protest a week ago in the capital calling for an independent probe into the disputed election.

According to official results, Hun Sen's Cambodian People's Party (CPP) won 68 seats in the July polls against 55 for the CNRP.

The opposition has rejected the result, alleging widespread vote rigging, but so far its efforts to challenge the outcome have failed and it has few options left in its bid to overturn Hun Sen's victory.

In a new setback, the Phnom Penh Municipal Court rejected a lawsuit filed by the opposition against top officials with the National Election Committee.

In a letter to the opposition party, seen by AFP, the prosecutor said the case was not under the court's jurisdiction.

The CNRP had accused three top NEC officials and their accomplices of faking voter names on the electoral roll, using "fake election results" and abusing the election law.

The discovery of several explosive devices in the capital on Friday added to tensions ahead of three days of planned opposition rallies starting from Sunday.

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

A former Khmer Rouge cadre who defected and oversaw Cambodia's rise from the ashes of war, his government is regularly accused of ignoring human rights and suppressing political dissent.

Rainsy, his main rival, was barred from running in the July elections because his name was removed from the electoral register last year following criminal convictions he contends were politically motivated.

He returned from several years of self-imposed exile in July after receiving a surprise royal pardon.

Previously he had faced 11 years in jail after he was convicted in his absence for charges including inciting racial discrimination and spreading disinformation.

CPP officials could not be reached for comment on Saturday.

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