Groups who once supported the president of Haiti, René Préval, are arming themselves against the government, putting the earthquake-ravaged country in danger of renewed instability and political violence.

Women queue for food at a homeless earthquake survivors' camp in Port-au-Prince. Photograph: Ramon Espinosa/AP Threats from individuals closely linked to a number of leading gangs who once enjoyed the patronage of former president Jean-Bertrand Aristide come amid growing private concern among diplomats and aid workers over Haiti's increasingly dangerous trajectory.

The country's parliament expires next month, but with no elections on the horizon Préval has moved to consolidate his control over the country's reconstruction. The Senate voted last week to extend the state of emergency by 18 months, creating a reconstruction commission to administer billions in aid that will be overseen by Préval and former US president Bill Clinton.

Despite pledges of billions in aid from the international community following January's earthquake - which killed 230,000 people - anger and resentment are growing against both the Haitian government and the international community. The anger is being driven by the widespread perception - three months after the catastrophe - that what aid and reconstruction money is coming into Haiti is benefiting the country's more articulate and wealthy minority, while not reaching the vast mass of victims of the quake. That, in its turn, has revitalised the country's long-existing political and social antagonisms between a huge and impoverished class and a tiny political and business elite.

Observers are also warning of the potential for social friction between those whose homes were destroyed, who are being furnished - often for the first time - with sanitation, food aid and schooling and those deeply impoverished shanty town dwellers who have not lost their homes, whose conditions are equally desperate.

The sense of an impending political crisis in the devastated country is also being exacerbated by the rapid corrosion of legitimacy in the Préval government - whose mandate runs out this year - and the lack of any obvious successor for a smooth handover of political power, something that has happened only twice in Haitian history.

The warnings of a worsening political situation have emerged amid a resurgence in gang activity in Port-au-Prince that has been reflected, say doctors, in a sharp increase in gunshot cases being treated at the main hospital.

The risk of a return to the kind of violence that once dogged Haiti was bleakly underlined last week. In one camp in sight of the ruined presidential palace, the Observer arranged to meet a group of anti-Préval activists, two of them with family connections to notorious gang leaders from the slums of Cité Soleil, who asked to be identified only by nicknames.

"There is a bigger group inside the camp who don't want to be identified," explained a man who asked to be called "Killer", who pulled down the band of his trousers to show a gunshot wound on his hip received in the fighting between UN troops and gang members in 2004. "We are going to fight Préval and the government. We have already got the guns. We have people here from Cité Soleil who want to fight. We're not going to live in this misery."

"We have many groups who are getting organised," said an older man who called himself "Danger". "Préval must go. And we are the people who helped him get elected."

"The biggest problem," added "To Bless", "is that Préval has not created jobs for the poor after the disaster. He hasn't come to see us and he has had nothing to say to us."

While all the men describe themselves as part of the Lavalas bloc that elected both Aristide and Préval, they say they are utterly disillusioned both with the Haitian government and the UN.

Asked about their political agenda, the men said they would prefer "an occupation" to manage the country's recovery, rather than their own leaders.

It reflects a survey of more than 1,700 Haitians released last week by Oxfam that revealed that fewer than 7% wanted their government to manage reconstruction on its own, though nearly 25% thought that it could work together with the local authorities and community organisations. Nearly 40% wanted control to fall to a foreign government. Yet in a separate question, fewer than half of the respondents thought the international community would follow through on its pledges.

The anger is also being driven by increased efforts to move a number of the larger camps, which is resented by many of the residents, who have said they will resist it.

While some international officials are sceptical whether those threatening violence have the capacity to organise themselves into a coherent political challenge, others believe that - post-earthquake - Haiti is in danger of tipping into a spiral of confrontation.

Indeed, recent major social crises in Haiti have required very little organisation, tapping instead into a deep and widespread sense of discontent in the impoverished nation.

Some observers also believe that those threatening violence are those who once benefited most from Haiti's troubled politics, being paid as guns-for-hire by senior political figures. Marginalised in the last couple of years, they have now been displaced by the earthquake to the city's squalid camps, and are furious that the government is no longer supplying those locations with food and other aid in an attempt to force them to move from where they have settled.

"It could go either way right now," said one international official, who asked to remain anonymous.

"Haiti is facing real dangers in the short term. The government has disappeared, as far as most Haitians are concerned. The state itself is very fragile. All I can say with any certainty is that all the ingredients for a social explosion are there.

"We are now seeing gangs back on the scene. But the biggest problem is people's perceptions, especially in the camps. Rightly or wrongly, they feel they've been abandoned."