SYDNEY (AFP) - One of Papua New Guinea's most notorious criminals escaped the country's main prison on Tuesday in his second breakout from the high-security unit in just over three years, police said.

Early reports said that more than 30 inmates had escaped from Bomana prison outside Port Moresby. But police spokesman Superintendent Dominic Kakas told AFP that only four men had escaped, with bank robber William Kapris among them.

"Only four escaped from prison; they are all high-risk prisoners," he said. "They are armed with about three firearms."

Supt Kakas said the details of the escape were not yet known but reports have suggested that Kapris led the break-out and may have had inside assistance.

Kapris, a bank robber who is considered a dangerous underworld figure, last escaped from the maximum security unit in January 2010.

That escape occurred when a woman posing as a lawyer smuggled a gun into the prison complex, helping to release 12 prisoners. Most of those who fled in that breakout, including Kapris, were recaptured within weeks.

A series of recent crimes has rekindled debate about harsher penalties for violent offences.

Central to the law and order push is reviving the death penalty, which is currently in place for treason, piracy and wilful murder but has not been used since 1954.