* Ageing leader's health puts question mark over future
* President is ally of U.S. against Islamist militancy
* Opposition frontrunner warns of ballot fraud (Adds details on victory claim, fraud charge)
By Lamine Chikhi and Patrick Markey
ALGIERS, April 17 (Reuters) - Algerian President Abdelaziz Bouteflika looked set to win a fourth term with allies claiming victory in an election on Thursday, despite questions over his health and his rare appearances since suffering a stroke in 2013.
Official results were due on Friday, but Bouteflika's camp claimed the independence veteran backed by the dominant National Liberation Front (FLN) party had succeeded in securing five more years at the helm of the North African OPEC state.
The 77-year-old Bouteflika, who has appeared in public only a few times since his stroke, earlier voted in Algiers while sitting in a wheelchair. He gave no statement and only briefly shook hands with supporters before leaving.
"Our candidate is the winner," Abdelaziz Belkhadem, Bouteflika's personal representative, told Reuters without giving any details. "Without any doubt, Bouteflika got a landslide victory."
Ali Benflis, Bouteflika's main rival in a field of opposition candidates struggling to challenge him, quickly rejected the election results because of fraud but did not cite any specific accusations.
"I do not recognise these results, I condemn this fraud," he said soon after the closing of the polls.
Algeria under Bouteflika has been seen as a partner in Washington's campaign against Islamist militancy in the Maghreb and a stable supplier of about a fifth of Europe's gas imports.
But concerns about Bouteflika's condition and how Algeria manages any transition have raised questions about stability in a region where neighbouring Libya, Tunisia and Egypt are still in turmoil after the Arab Spring revolts of 2011.
Loyalists portray Bouteflika as the man who helped stabilise Algeria after a war with Islamist militants in the 1990s that killed around 200,000 people.
But several opposition parties have boycotted the vote - including rivals the Islamist MSP and secular RCD - saying it is slanted in Bouteflika's favour and unlikely to bring reforms to a system little changed since independence from France in 1962.
Bouteflika, a veteran of Algeria's war of independence, won the 2009 election with 90 percent of the vote. In 2004, Benflis lost to Bouteflika in a ballot he said was tainted by fraud on an "industrial" scale.
"No country is 100 percent good, but the things he has done, he has done well," said Abdessaid Said, a retired technician who voted for Bouteflika in Algiers' Bab El Oued district.
"I know he is ill, but I vote for him for what he has done for us. And he can still govern."
Voting passed mostly peacefully, but in two villages east of Algiers, gendarmerie troops fired tear gas and clashed with youths who tried to disrupt voting, local officials said.
Several ballot boxes were burned in the area, which is a stronghold of an opposition party boycotting the election and also a mostly ethnic Berber-speaking region that sees sporadic clashes with authorities.
Police on Wednesday broke up a small rally by an anti-government movement called "Barakat", or "Enough", which is calling for peaceful change with rare public protests.
CALLS FOR REFORM
Since the stroke that put him in a Paris hospital for three months, Bouteflika has appeared only a few times in public, usually when speaking with visiting dignitaries. He did not campaign, though allies say he is well enough to govern.
Opposition leaders say it is time for him to make good on promises to hand over to a new generation of leaders, tackle corruption and open up an economy hampered by restrictions dating back to Algeria's post-independence socialism.
Many Algerians say that since independence, their politics has been controlled by a cabal of FLN elites and army generals who, while competing behind the scenes for influence, see themselves as guarantors of stability.
Bouteflika's allies have tried to strengthen his position by reducing the influence of the powerful military intelligence chief, who for years played the role of kingmaker.
Still, analysts say, political rivalries may resurface if Bouteflika's health ebbs during a fourth term.
His allies are promising constitutional amendments to open up a system that critics say has resisted reform since the old guard of FLN chieftains won independence from France.
But many younger Algerians say they feel disconnected with their country's political leadership.
"I have decided not to vote because I'm fed up with promises," said Ahmed Djemi, drinking coffee in Bab El Oued district, complaining that he has been waiting for years to get an apartment.
Riots and protests over services, housing and food costs have erupted, but the opposition remains divided and unable to challenge the dominance of the FLN, its allies and unions.
The state has built up huge foreign reserves from its energy sales - around $200 billion - and has spent heavily on subsidies and social programmes to ward off Arab Spring-style protests.
Analysts say the country needs reforms to overhaul an economy hampered by restrictions on foreign investment and to attract more heavyweight petroleum players to boost stagnating oil and gas production. (Additional reporting by Hamid Ould Ahmed and Lamine Chikhi; Editing by Tom Heneghan and Ken Wills)