A hat with the word “Gangster” written on it lies on a sidewalk near a bank in Melbourne, Australia. More than two dozen people were injured in an arson attack on the bank branch. (Julian Smith/ EUROPEAN PRESSPHOTO AGENCY )

When thousands of South Sudanese refugees arrived in Australia’s second-largest city in the 2000s, Melbourne offered a welcoming haven from the civil war in their homeland.

But more than a decade later, some of those refugees — and their teenage children, born here — have formed criminal gangs of alienated young black men. Advocates for the refugees say that Australia hasn’t provided them with the opportunity to assimilate or find legitimate opportunity, and that they represent a small portion of the refu­gee community. The news media has made much of the crimes blamed on these gangs, and each incident adds fuel to a backlash against Australia’s refugee program in one of its most liberal cities.

In October, three African Australians, armed with a hammer, a machete and a gun, robbed a jewelry store in a busy shopping district in the city’s ritziest suburb. They got about $200,000 worth of merchandise. The midday theft made the front pages.

Australians’ feelings about refugees are a paradox: A wealthy country proud of assimilation of migrants over its 228-year history, Australia resents the thousands of people who have made the treacherous trip by sea to seek refuge here.

Sixty-one percent of Australians disapprove of people who arrive by boat seeking asylum, many of whom are escaping wars or persecution in Afghanistan, Iraq and Sri Lanka, an annual survey by Monash University academic Andrew Markus published last week found.

Simultaneously, detention centers built in the island state of Nauru and Papua New Guinea to deter asylum seekers are regarded by many Australians as their greatest national shame.

About 1,300 men, women and children seeking asylum in Australia, or already classified as refugees, have been forced to wait in Papua New Guinea and Nauru by the Australian government for homes to be found for them. Some have been there for years, a situation condemned by the United Nations High Commissioner for refugees and dozens of human rights, legal and medical organizations.

Prime Minister Malcolm Turnbull and U.S. Secretary of State John F. Kerry recently said that the genuine refugees among them would be allowed to relocate to the United States after being screened by the U.N. refugee agency.

If the incoming Donald Trump administration honors the agreement, it will be a major achievement for Turnbull.

Turnbull argues that a tough approach on boat arrivals boosts public support for admitting refugees who wait patiently overseas for their claims to be processed. In September, he said a one-time 36 percent increase in refugees to 18,750 announced by his predecessor would be made permanent. But any asylum seeker who tried to get to Australia by boat would never be allowed onto Australian soil, he said, even as tourists well into the future, a decision condemned by the opposition Labor Party as draconian.

“If we wish to stop people drowning at sea, if we wish to put the people smugglers out of business, if we wish to maintain one of the most generous humanitarian refugee programs in the world, we must maintain the integrity of our borders,” Turnbull said recently.

At the start of the century, Australia helped relieve the pressure on camps in the Horn of Africa by admitting thousands of refugees from the South Sudanese civil war. Between 2003 and 2005, 70 percent of all refugees allowed into Australia were African.

With little English, education or experience of Western society, the largest group of Sudanese settled in Melbourne, a predominantly white, Christian city in the southeast of the continent known for its coffee shops and love of Australian Rules Football. They were provided with housing, education and access to Australia’s generous social security system, including free health care.

As those refugees’ children grew into teenagers, some joined gangs that are now driving a statewide increase in crime, including car jackings and home invasions. One crime in vogue is ramming the rear of another car and stealing it when the driver gets out to exchange addresses, police say.

In March, dozens of African Australian teenagers and young men went on a rampage through Melbourne’s biggest family event, an annual Labor Day parade called Moomba. They threw chairs, picked fights and damaged property.

Even though gangs with Sudanese members had been targeted by police over the previous year, video and cellphone footage of aggressive young black men running in groups through the city’s downtown area unnerved the city.

“We are not used to this kind of mob behavior on our streets,” the chief commissioner of the state’s police force, Graham Ashton, told a summit he called to discuss the problem.

Community leaders, knowing the position of refugees in their host society is inherently fragile, are embarrassed. “It damages the reputation of the rest of my South Sudanese countrymen,” said Ambrose Mareng, the chair of the South Sudanese Community in Australia, in an interview. “We appreciate all this country has done for us.”

The problem, Mareng and other experts say, is common to almost any new immigrant community: marginalized and angry young men with few prospects for advancement.

“If you are a black and even if you have a qualification — we have lots of young people who can’t get interviews and can’t get a job,” said Carmel Guerra, chief executive of the Center for Multicultural Youth, a Melbourne charity that works with African teenagers and others, in an interview.

The head of Australia’s border force suggested in April that gang members be deported. But Ashton, the police commissioner, said that was unrealistic because many were too young, their crimes were not serious enough or they were born in Australia.

The main official response is to allocate more resources to policing. A police task force directed at the gangs has arrested about 215 people in six months.

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