Talks between Spain's Iberdrola SA (IBE.MC) and other shareholders of Neoenergia SA (GNAN3.BR) about accumulating a majority stake in the Brazilian utility are at an advanced stage, a spokesman for the Spanish power company said.

Iberdrola currently has a 39% stake in Neoenergia and has been in talks with other shareholders about buying some of their interests for months, the spokesman said.

On Tuesday, Bloomberg News reported that Iberdrola had offered about EUR1.5 billion to boost its Neoenergia stake to 75%, citing people close to the matter. A spokesman for Iberdrola told Dow Jones Newswires he couldn't confirm the figures.

-By Ilan Brat, Dow Jones Newswires; +34913958125; ilan.brat@wsj.com