* Young members of ruling party brawl with knives
* Ministers criticise head of FLN party, a presidential ally
* Party chief says crisis invented by the media
ALGIERS, Oct 21 (Reuters) - Senior members of Algeria's ruling party have criticised the party leader, an ally of President Abdelaziz Bouteflika, in a rare show of dissent that could challenge the head of state's authority.
Cracks appeared in the usually tightly-disciplined FLN after press reports said young members had brawled with party officials in some areas, at times with knives, and a minister asserted that the party leader had lost control and should quit.
Abdelaziz Belkhadem, head of the FLN (Front de Liberation National) and also a member of the government with the portfolio of Bouteflika's personal representative, said "it is a crisis which exists only in the media."
But analysts said that because Belkhadem is so close to the president, the divisions inside the party -- of which Bouteflika is honorary president -- could add to perceptions among some that he is losing influence to rivals inside the ruling elite.
"The current crisis will weaken Bouteflika's authority," said Mohamed Lagab, a political analyst and teacher of political sciences at Algiers' university.
Algeria, a member of OPEC, supplies about a fifth of Europe's energy needs and is also the world's eighth biggest crude exporter.
The FLN infighting began when young party supporters in several regions clashed violently with local party officials in arguments about who would be given influential party posts in a re-organisation of local offices.
There were some injuries in the violence but no reports or arrests or prosecutions. The incidents occurred over several days up until Wednesday, the reports said.
They prompted El Hadi Khaldi, minister for vocational training, to speak out against Belkhadem.
"We must do something to stop the fight inside the party which is due to Belkhadem's contradictory instructions to the membership," Khaldi was quoted as saying by El Khabar newspaper. "He should follow his predecessors (and step down) ... to stop members of the party from fighting."
Other serving and former government ministers who are FLN members have also spoken out in local media against Belkhadem.
The FLN, which has been in or close to the centre of power since Algeria's independence from France in 1962, controls the parliament and has a majority of ministers in the government.
"The fact that several ministers are against their boss (Belkhadem) is troubling. They can't do what they are doing without getting a green light from influential circles," Nacer Jabi, a political analyst who has written extensively about the FLN, told Reuters.
"I am not sure they got the green light, and if they got it, we need to make sure they have understood it," Jabi said.
Analysts say Bouteflika, 73, has been weakened in the past year by the departure of close allies from government.
In a reshuffle, Energy Minister Chakib Khelil was fired and ex-interior minister Nourredine Zerhouni was moved to the post of deputy prime minister, in which he wields less real power.
The shifts could be a warning signal from some in the government apparatus who believe that Bouteflika and his allies have amassed too much power, some analysts say.
(Editing by Mark Heinrich)