Vicious drug gangs and the lawlessness they have created are driving thousands of Central Americans to flee their countries and seek refuge overseas, including, now, Australia.

Prime Minister Malcolm Turnbull announced, in front of world's leaders at a refugee summit at the UN in New York, that refugees processed by the UNHCR in Costa Rica will be offered asylum as part of Australia's annual intake.

"We seek to work with other countries. We're seeking always to provide resettlement options wherever we can," Mr Turnbull said.

"Australia is a very generous humanitarian nation in the way in which we treat and receive refugees. So, we've got every reason to be proud of that."

Gloria Maklouf, the director of Costa Rican-based refugee agency ACAI, said: "Australia? It's a surprise, but we're grateful."

"We get many families who are fleeing the forced recruitment of the Maras," she said.

Arrested members of Mara Salvatrucha flash their gang's hand sign from inside a jail cell. ( Reuters: Ulises Rodriguez )

'It's simply terror'

Those "Maras" are the two main gangs — MS-13 (Mara Salvatruchas) and MS-18 (18th Street gang).

Their main force is in the US, but internationally they number in the tens of thousands and are easily identifiable for their heavily tattooed bodies and strange sign language.

The FBI has had a specific MS-13 gang task force since 2004 because it has infiltrated almost every American state.

The gangs have their origins in the suburbs of LA in the 1990s in the post-civil war periods of El Salvador, Honduras and Guatemala — "the northern triangle".

Many were extradited back to those countries, where they continue to cause carnage on a daily basis.

In El Salvador, after a peace deal between the gangs and the government broke down, the murder rates skyrocketed — Honduras also has some of the highest murder rates anywhere on the planet outside the civil war in Syria.

"It's simply terror. The organised criminals are growing ever stronger," Ms Maklouf said.

"They target boys aged 10 to 15 for recruitment. The families, at the first sign or threat, they pack up and flee overnight.

"The girls also suffer from persecution because the Maras want them for gangs.

"If you have a business, big or small, they will extort you — if you don't pay they will kidnap family members or kill them.

"These refugees just pack up and go no matter what time of day it is.

"Some try to go somewhere else in their countries, but, for example, El Salvador is so small that they can find them within a fortnight. So they leave to Costa Rica."

All they need to enter is a passport.

Members of the 18th Street gang at the Cojutepeque Jail. ( AFP: Jose Cabezas )

'We will watch with caution'

In the past many fled north — the situation became so bad in these three nations that thousands of unaccompanied children walked and caught trains through Mexico, crossing into the US, in 2014, causing a humanitarian crisis for the Obama Government.

US actions, along with Mexico's tough enforcement of its southern border, have stopped that influx.

Costa Rica used to have more than 10,000 refugees from Columbia and Cuba, but now it has about 4,000 — most from Central America — and Ms Maklouf estimates another 4,000 being processed.

Her organisation gives the refugees food, accommodation and basic necessities, as well as helping them to find work and psychological support.

"We'd like to know more about Australia's offer. I'd worry about what their [the refugees'] expectations are," she said.

"Many have relatives in the US who can help them integrate. Australia is possibly not as hospitable for them.

"We don't know what expectations they could have. Even here in Costa Rica it's not easy for them to integrate.

"We will watch with caution how this process works itself out. They will need to be well informed to make a decision."