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Despite mass protests, accusations of rigged elections, a brief hunger strike by a prince and a threatened boycott of parliament by his rivals, Cambodia's long-ruling strongman Hun Sen remains firmly in control.

But after his worst poll result in 15 years and a series of demonstrations drawing tens of thousands of people, experts say the former Khmer Rouge fighter-turned-premier must now realise that something has to change.

"Hun Sen got a huge kick -- a huge wake-up call -- during the election," said Ou Virak, president of the Cambodian Center for Human Rights.

"So I think Hun Sen is getting the message that people are not happy with the way he runs the country."

Three days of demonstrations descended into violence earlier this month when a protester was shot dead as security forces clashed with a stone-throwing crowd.

Cambodia's political crisis faces a crucial juncture this week with the opposition set to boycott parliament when it convenes on Monday unless Hun Sen agrees to its demand for an independent probe into the disputed July polls.

Several rounds of talks between Hun Sen and opposition leader Sam Rainsy over the past week failed to break the deadlock, raising fears of a protracted dispute and further mass protests.

The two sides agreed to seek a non-violent solution to the impasse and made a vague pledge to set up a mechanism to bring about election reform.

The key demand of the opposition Cambodian National Rescue Party (CNRP) is for an independent "truth committee" to investigate Hun Sen's controversial election victory. On that, the premier has refused to budge.

The crisis took a new twist on Friday when a pro-opposition Cambodian prince -- the cousin of King Norodom Sihamoni -- went on hunger strike in protest at Hun Sen's contested win, demanding "justice for voters".

His protest ended Saturday after military police expelled him from the pagoda where he was holding the hunger strike.

Experts say that ultimately the emergence of a more vocal and emboldened opposition should be positive for a country that has been run almost single-handedly by Hun Sen for 28 years.

"We're moving towards a two-party system, which is good for the country, for a healthy democracy," said independent analyst Lao Mong Hay, a former researcher for the Asian Human Rights Commission.

According to official results of the July election, the Cambodian People's Party (CPP) won 68 seats against 55 for the CNRP.

The opposition has rejected the tally, alleging widespread vote irregularities.

The CNRP has warned of further protests unless Hun Sen agrees to its demands, which also include an overhaul of the National Election Committee.

The question now, say experts, is how much ground Hun Sen will be willing to cede to the opposition, and how his rivals will use their new-found political clout.

"The natural role of the opposition in Cambodia in the past has been defensive, the role of a victim, impulsive and not very disciplined," said Jackson Cox, an analyst with the consultancy firm Woodmont International.

"They should and must demonstrate they are not the opposition party of the past. They have to act proactively."

The CNRP faces a dilemma -- if it refuses to compromise it risks losing its voice in parliament.

But if it strikes a deal with Hun Sen that leaves the strongman in power, then it could face a backlash from its supporters who appear hungry for change.

"I want justice because people voted for CNRP," said opposition supporter Hok Rim, 32. "If there's no solution, I'm ready to join more protests."

From land-grab protests to strikes in the key garment sector, public discontent shows that Hun Sen can no longer rely on his image as a liberator from the horrors of the Khmer Rouge to underpin support, experts say.

Hun Sen is 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.

While garment exports and tourism have brought double-digit economic growth, Cambodia remains one of the world's poorest countries, and younger Cambodians are also increasingly intolerant of endemic corruption.

But experts say the 61-year-old premier -- who has vowed to rule until he is 74 -- is unlikely to relinquish his grip of power yet.

"Hun Sen will want to take the moral high ground and appear to be cooperating in the interest of national unity and reconciliation," said Carl Thayer, professor at the University of New South Wales in Australia.

"But he will not let political reforms undermine the basis of his power."