The Abbott government wants to send some asylum seekers to Cambodia, at a time when the country's strongman prime minister, Hun Sen, is overseeing a brutal crackdown on dissent in one of south-east Asia's poorest nations.

Facing growing opposition after decades of authoritarian rule, Hun Sen last month authorised a violent crackdown on anti-government protesters and striking garment workers that left five people dead and dozens injured.

A request on Saturday by Australia's foreign minister, Julie Bishop, for Australia to initially send a small group of asylum seekers to live in Cambodia comes amid the strongest challenge to Hun Sen's rule since he took power in 1985, becoming one of the world's longest-serving leaders, with a reputation as a wily operator who destroys his political opponents.

Before the visit, Human Rights Watch urged Ms Bishop to put rights abuses at the top of her agenda in meetings with Cambodian leaders, saying under Hun Sen's rule, ''basic rights, such as freedom of expression, assembly and association, are under regular attack, while corruption is rampant, severely affecting the enjoyment of basic economic and social rights by a very poor citizenry''.

''Australia has claimed credit for its diplomacy in the 1990s that was supposed to lead to a democratisation of Cambodia based on respect for human rights. Sadly, that has not materialised,'' said Elaine Pearson, Australian director at Human Rights Watch.

Hun Sen, a former cadre of the murderous Khmer Rouge, often uses his country's security forces, judicial system and other key national institutions for political purposes, rights groups say.

As demonstrations grew following an election last July that opposition parties claim was unfair, the 61-year-old banned freedom of assembly, prompting the often-violent dispersal of protesters.

Authorities have held 23 people arrested during a garment workers' strike incommunicado without proper medical care in a remote prison since January 3.

If an agreement is reached with Australia, asylum seekers would arrive in a country that has no social welfare and where 20 per cent of the population live in poverty and 40 per cent of children under the age of five are malnourished, according to the World Bank.

But the bank says poverty has fallen sharply in recent years, underpinned by the garment industry, private investment and growth in the agriculture sector.

Cambodia is one of only two south-east Asian nations to have signed the 1951 Refugee Convention and has had a strong UN presence since an Australian-brokered UN peacekeeping operation in 1992-93. During the past four years, Australia - one of its largest aid donors - has provided more than $329 million.

Canberra was also quick to recognise Hun Sen's election victory, despite claims of voting irregularities.

During her two-day visit, Ms Bishop gave no details publicly of Australia's request, referring only to talks on the Bali Process on people smuggling and trafficking, a multi-country gathering that deals with asylum-seeker issues.

But her Cambodian counterpart, Hor Nam Hong, said his country would seriously consider the request.

Opposition immigration spokesman Richard Marles said on Monday that Australians were finding out more about this proposal from the foreign media rather than the Foreign Minister.

Asked whether it was appropriate for Ms Bishop to ask one of the poorest countries in Asia, Cambodia, to take asylum seekers from Australia, Mr Marles said there was not enough detail available to say anything definitive.

''Right now we know more about this from the foreign media than from the Foreign Minister,'' Mr Marles told ABC radio.

''We've got to see exactly what is being proposed . . . and the opposition will have a good look at whatever that proposition is.''

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