Australia's prime minister has called human-traffickers the "scum of the earth", after defending his government's immigration policies.

Kevin Rudd's comments come after three people died in an explosion on a boat sailing off the Australian coast which was packed with Afghan asylum-seekers.

Two people are still missing and another five are in a critical condition due to the explosion, according to hospital officials.

Rudd said: "People-smugglers are the vilest form of human life, they trade on the tragedy of others and that's why they should rot in jail and, in my own view, rot in hell."

Australia's conservative opposition party has blamed the deaths on a "softening" in immigration policy last year which is being seen as encouraging immigrants to attempt to get into Australia.

Australia's previous immigration policy, which had allowed asylum-seekers to be held in camps for long periods, had invited widespread criticism domestically.

Rudd defended the government's policy, saying: "This government is absolutely committed to dedicating all resources necessary to...maintain a hardline, tough and targeted strategy for maintaining this country's border protection."

Border protection

Rudd said that his government had dedicated more resources to combat traffickers  paid by asylum-seekers - many of whom come from Indonesia - than any other past Australian government. In Australia, convicted human traffickers currently face a maximum penalty of 20 years in jail.

In July 2008, the government eased the strict immigration policies by changing the system which regularly held asylum seekers, including children, in detention centres for years on end. Since then, 13 boats carrying more than 400 people have arrived in Australian waters.

Today's law requires that asylum-seekers are held on Australia's Christmas Island and that their cases, which must be expedited, are reviewed by an ombudsman every six months.

The cause of the explosion is not yet known, but the premier of Western Australia has said that the boat had been doused with fuel before the blast, suggesting the passengers had sabotaged their own vessel.

Philip Ruddock, the former immigration minister, told The Australian newspaper on Friday that intercepted boats were often disabled by the passengers who believed the act would prevent them from being sent back to their country of origin.

Indonesia's migrants

Australia has seen a growing trend in illegal arrivals by sea. Refugees fleeing from Afghanistan and Iraq have provoked a national debate about how to treat refugees.

Also on Friday, Indonesia detained 70 illegal migrants from Afghanistan with plans to travel to Australia in the second such arrest in recent months.

Two women and four children were among those held in Cilegon in Java Island just south of Jakarta, R Muchdor, the director of investigation and enforcement at Indonesia's immigration office, said.

As Indonesia struggles to cope with an increased number of migrants this year, Canberra and Jakarta have been holding ongoing negotiations on how to revise current laws to tackle human-trafficking.