Profile: Cambodia's Hun Sen
Cambodia's Hun Sen has been in power since 1985 and is one of the world's longest-serving prime ministers.
He is credited with helping achieve economic growth after the devastation caused by the Khmer Rouge regime, responsible for one of the worst mass killings of the 20th century.
But the prime minister, 60, is also seen as an authoritarian figure with a poor human rights record and the resources to thwart any real political challenge.
He shows no signs of wanting to relinquish power - in May he said he wanted another decade at the top.
His ruling Cambodia People's Party (CPP) is expected to dominate elections on 28 July 2103, most likely extending his leadership, despite the return of opposition leader Sam Rainsy.Political deals
Born into a peasant family in 1952, Hun Sen was educated by Buddhist monks in Phnom Penh.
In the late 1960s, he joined the Communist Party, and for a while he was even a member of the Khmer Rouge - although he denies accusations that he was any more than an ordinary soldier.
He lost his left eye during an exchange of gunfire and he has reportedly said he can only see a limited distance.
During Pol Pot's tyrannical regime in the late 1970s, under which as many as two million people died, Hun Sen fled to Vietnam to join troops opposed to the Khmer Rouge.
When Vietnam installed a new government in Cambodia in 1979, he returned as minister of foreign affairs, becoming prime minister in 1985 at the age of 33.
Hun Sen lost the 1993 elections, but he refused to accept the results and forced a negotiation to become second prime minister alongside the Funcinpec Party's Prince Norodom Ranariddh.
He went on to seize power in a bloody coup in 1997, forcing Prince Ranariddh to temporarily leave the country.
The CPP won general elections in 2003 but did not have two-thirds majority, so it struck a deal with Funcinpec in 2004, ending almost a year of political deadlock. Hun Sen was re-elected prime minister by parliament in July 2004.Rights criticism
In Cambodia's 2008 elections the CPP won most of the contested seats. But the polls were criticised by international monitors, with the EU saying the ruling party made "consistent and widespread" use of state resources for its own campaign.
Rights groups have also regularly criticised the country's human rights situation.
"The human rights situation in Cambodia deteriorated markedly in 2012 with a surge in violent incidents, as the ruling Cambodian People's Party (CPP) prepared for national elections," Human Rights Watch said.
At least 35 rights activists "opposing land grabs and demanding better working conditions were killed, wounded, arbitrarily arrested, threatened with arrest, or kept in exile by CPP-led security forces and the CPP-controlled judiciary".
Ahead of these elections, Hun Sen faced calls from the US to allow his main rival, Sam Rainsy, to return.
A royal pardon was subsequently granted to Mr Rainsy, who had been living abroad after being jailed in absentia on charges he said were politically motivated.
Mr Rainsy returned to Cambodia but remains unable to run in the polls on a technicality. And observers say that the conditions for a fair election do not exist because of the CPP's tight control over the media, judiciary and other key state organs.
Hun Sen has not campaigned for his re-election bid.
"I will not participate during the campaign. I don't want to face confrontation because during that time of year many people will criticise the CPP," he said.
But in a speech in June he said Cambodians should keep the polls from "breaking our nation, society, village and family".
"I am calling on all of our people and officials not to retaliate to acts of insulting [from opposition parties]."
"If they insult us... you just kindly and politely respond: 'For me, I think the Cambodian People's Party is good because it saved people from the genocide regime of Pol Pot, rebuilds the country. I wonder if I have seen the opposition party has done anything for the country so far'."