A manhunt is under way for Papua New Guinea's most notorious bank robber, William Kapris, who has escaped from the country's main prison along with three others, police say.
Police launched the search for Kapris shortly after he escaped from Port Moresby's Bomana prison at 5pm NZT on Tuesday.
"He had two guns," a police media spokesman told AAP.
"Kapris was the one who led the break out.
"These prisoners are high-risk prisoners, the worst of the worst."
He could not say how Kapris or the other prisoners escaped.
"He definitely had inside assistance," the spokesman said.
Deputy Police Commissioner and Chief of Police Operations Simon Kauba said a manhunt is under way to hunt down the escapees.
Police had earlier said 33 inmates had escaped, but then radically revised down the figure to four, including Kapris.
The break-out will be thoroughly investigated and anyone who had any role to play in the escape will be severely dealt with, Kauba said in a statement.
Kapris is known in PNG for a series of robberies at Bank of the South Pacific branches.
This breakout marks Kapris's third high-profile escape from authorities.
In 2010, the country's most wanted serial bank robber escaped from custody in a Toyota truck after taking a warder hostage.
He was aided that time by a woman who, posing as a lawyer, pulled a gun on guards.
He was rearrested a short time later along with several jail staff who allegedly assisted his escape.
It was not the first time Kapris had escaped PNG's justice system.
Before being captured in 2008, he had been on the run for eight years after escaping police detention while convalescing at Port Moresby General Hospital.
The news comes as PNG's legislators prepare to debate tougher penalties for violent crime in the nation's parliament, including reactivating the country's dormant death penalty.