"We are frustrated and tired of waiting," warned Afonso Henriques Fula, 52, one of the thousands of veterans currently gathering in the capital Luanda.

"If the government does not act before the elections, we will prevent them from taking place," the ex-fighter for the ruling MPLA said.

It is a threat Luanda cannot afford to ignore, given the strength of former combatants scattered across the vast African nation.

Official figures put the number of war veterans drawn from the three liberation movements MPLA, UNITA and FNLA at 40,000. But the total number in the country of 18 million inhabitants is thought to be much higher.

"The veterans are asking the government to recognise the sacrifices they made for the country, by providing them with a means of living," said Silva Mateus, a retired general who has written to President Jose Eduardo dos Santos to back the former soldiers' grievances.

Angola's veterans fought for independence from Portugal from 1961 to 1975, then battled each other in a civil war that lasted until 2002.

Public shows of dissent are rare in the tightly controlled country, where dos Santos has governed for more than three decades. But displeasure sparked youth rallies over a year ago demanding he step down, and now other sectors of society are taking to the streets.

In June, soldiers and riot police unleashed water cannons and dogs to disperse the war veterans when they staged protest marches on the presidential palace and the defence ministry.

Veterans of the region's liberation wars have long wielded considerable political clout across southern Africa, not least in Zimbabwe where they have been at the vanguard of the seizures of white-owned farms.

Many former fighters in Angola, like Fula, are in limbo because they have yet to be formally demobilised, so remain without their discharge bonuses and monthly pensions.

They say that Angola, which is bursting with reconstruction projects and oil wealth, can afford to pay them. The country's economy is ranked among the world's fastest growing and Angola is Africa's second-largest oil producer.

The protests unnerve authorities, who fear they could easily feed into other frustrations dogging a nation buckling under high levels of unemployment, insecurity and the high cost of living.

"These protests are also evidence of the beginning of citizens' awareness of their rights and how they can exercise them, a right guaranteed by the constitution," Serra Bango of the Association of Justice, Peace and Democracy said.

Dos Santos is seeking another term in office in elections set for August 31, which will be only the third in the country's history.

"I was demobilised in 1992 after the signing of the Bicesse Peace Accords. At the time, the government promised financial guarantees and vocational rehabilitation assistance," said Jose Rodrigo Pessoa, 44, who fought for FAPLA, the armed wing of the ruling People's Liberation Movement of Angola, or MPLA.

Shortly after this accord, conflict flared up again, only to end again 10 years later.

"But until today I have received nothing," said the father of seven, who is now a construction worker.

"We just have two meals a day ... and if someone falls sick, I have to ask for help from my family to pay the doctor," Pessoa said.

His is the typical daily grind for all ex-soldiers, whose uncertain discharge status further complicates their search for jobs.

In addition to the lump-sum demobilisation bonuses of about 55,000 kwanzas ($550, 450 euros), the former fighters want a monthly retirement stipend, a benefit so far granted only to senior officers.

"This money is not for us who are old, and wasted our time in combat, it's to pay school fees for our children to study and have a future," said Lino Manuel, 56, a former sergeant who was wounded in the right leg during the war. He still suffers pain.

When the protests started, the defence ministry called for calm and promised to pay each veteran $500 (400 euros) a month.

Human Rights Watch has accused Angola of an "alarming" crackdown on war veterans and youth protesters amid a growing public show of dissent in the run-up to the polls.