UPDATE 1-Belgacom to appeal 66 mln euro antitrust fine

* Chief executive says group will appeal fine

* Says partial provisions for fine had been made

(Adds details)

BRUSSELS, May 27 (Reuters) - Belgium's dominant telecom operator Belgacom (BCOM.BR) said on Wednesday it would appeal a record 66.3 million euro ($92.6 million) fine imposed by the Belgian competition authority for abusing its dominant position.

The Belgian Competition Council on Tuesday said that in 2004 and 2005 the group's mobile phone arm Proximus charged its end-users lower prices than the wholesale prices it charged to competitors to use its network.

"This is completely wrong. We never sell at a loss to recuperate the losses from another client," Belgacom Chief Executive Didier Bellens told a news conference on Wednesday.

Bellens also said the competition authority's findings contradicted previous claims that it was selling the services at a loss.

"You cannot say that our prices are too high, and then say that we are making a loss," Bellens said.

The council determined that Belgacom's "margin squeeze" constituted abuse of a dominant position, an infringement of Belgian and European Union competition rules.

"Competitors were unable to propose prices to their clients for communications towards the Proximus network that were more interesting or even similar to the prices that Proximus could offer to its clients," the council said.

Belgacom must pay the fine within 30 days but could reclaim it if the appeal succeeds, a lawyer for the company said.

Bellens said Belgacom had made partial provisions for the fine in previous years.

The fine follows a complaint in 2005 by rival Base, owned by Dutch peer KPN (KPN.AS), which alleged Proximus had deliberately excluded its rivals, particularly for business customers.

Belgacom shares ended the day down 0.3 percent at 22.3 euros, compared with a 0.6 percent rise in the DJ European telecoms index. .SXKP (Reporting by Antonia van de Velde; editing by Karen Foster)